RESUMO
Uroporphyrinogen decarboxylase (UroD) (EC 4.1.1.37) is an enzyme from the tetrapyrrole biosynthetic pathway, in which chlorophyll is the main final product in algae. This is the first time that a study on UroD activity has been performed in a green alga (Chlorella). We isolated and partially purified the enzyme from a Chlorella kessleri (Trebouxiophyceae, Chlorophyta) strain (Copahue, Neuquén, Argentina), and describe for the first time some of its properties. In C. kessleri, the decarboxylation of uroporphyrinogen III occurs in two stages, via 7 COOH and then 6 and 5 COOH intermediates, with the decarboxylation of the 7 COOH compound being the rate-limiting step for the reaction. Cultures in the exponential growth phase showed the highest specific activity values. The most suitable conditions to measure UroD activity in C. kessleri were as follows: 0.23-0.3 mg protein/mL, approximately 6-8 micromol/L uroporphyrinogen III, and 20 min incubation time. Gel filtration chromatography and Western blot assays indicated that UroD from C. kessleri is a dimer of approximately 90 kDa formed by species of lower molecular mass, which conserves enzymatic activity.
Assuntos
Chlorella/enzimologia , Uroporfirinogênio Descarboxilase/isolamento & purificação , Chlorella/crescimento & desenvolvimento , Peso Molecular , Uroporfirinogênio Descarboxilase/imunologia , Uroporfirinogênio Descarboxilase/metabolismoRESUMO
BACKGROUND: Inherited and environmental factors are implicated in the expression of porphyria cutanea tarda (PCT); the contribution of each factor depends on the population. OBJECTIVE: To provide a review of PCT cases diagnosed in Argentina over 24 years and evaluate the role of different precipitating factors in its pathogenesis. Methods Plasma and urinary porphyrin levels and erythrocyte uroporphyrinogen decarboxylase (URO-D) activity were determined. Potential precipitating factors were identified in each patient. Additional tests for hepatitis C virus (HCV) and hemochromatosis gene mutations were carried out. RESULTS: Several factors (mainly alcohol abuse in men and estrogen ingestion in women), alone or combined were identified in our patients. Prevalence of HCV infection was 35.2%. Inherited URO-D deficiency occurs in 25.0% of cases. H63D was the most common hemochromatosis gene mutation. High incidence of PCT associated with HIV infection was found. CONCLUSIONS: PCT is multifactorial. Therefore, knowledge of all risk factors in each patient is important for the management of the disease.
Assuntos
Porfiria Cutânea Tardia/etiologia , Adolescente , Adulto , Idade de Início , Idoso , Argentina/epidemiologia , Criança , Feminino , Proteína da Hemocromatose , Hepatite C/fisiopatologia , Anticorpos Anti-Hepatite C/sangue , Antígenos de Histocompatibilidade Classe I/genética , Humanos , Masculino , Proteínas de Membrana/genética , Pessoa de Meia-Idade , Mutação , Porfiria Cutânea Tardia/epidemiologia , Porfiria Cutânea Tardia/genética , Fatores Desencadeantes , Estudos Retrospectivos , Fatores de Risco , Uroporfirinogênio Descarboxilase/metabolismoRESUMO
Uroporphyrinogen decarboxylase is an essential enzyme in all organisms and functions in the heme biosynthetic pathway, catalyzing the decarboxylation of the four acetate groups of uroporphyrinogen to form coproporphyrinogen. This work examines whether the four sequential decarboxylations occur at the same active site, and explores whether hexachlorobenzene-induced porphyria affects the behavior of the enzyme. For this purpose, kinetic competition studies were done with mixtures of uroporphyrinogen III and pentacarboxyporphyrinogen III. With the enzyme from normal rats, a constant velocity was obtained with all the mixtures, indicating that uroporphyrinogen and pentacarboxy-porphyrinogen react at the same active site, i.e. the first and fourth decarboxylations occur at the same site. In contrast, in experiments with enzyme from rats with hexachlorobenzene-induced porphyria, the total rate for mixtures was always lower than the reference rate; and a curve with a deep minimum was obtained, indicating that the two reactions occur at functionally different sites, but with cross-inhibition. This suggests that the modifications induced in the enzyme by hexachlorobenzene cause the two active sites to become nonequivalent and functionally different. The question is discussed how the hexachlorobenzene treatment may produce this abnormal kinetic behavior, and alternative hypotheses are considered.
Assuntos
Hexaclorobenzeno/farmacologia , Porfirias/induzido quimicamente , Porfirias/enzimologia , Uroporfirinogênio Descarboxilase/metabolismo , Animais , Feminino , Hexaclorobenzeno/toxicidade , Cinética , Fígado/efeitos dos fármacos , Fígado/enzimologia , Porfirinogênios/metabolismo , Ratos , Ratos Wistar , Uroporfirinogênios/metabolismoRESUMO
The porphyrias are heterogeneous disorders arising from predominantly inherited catalytic deficiencies of specific enzymes in heme biosynthesis. Porphyria cutanea tarda (PCT) results from a decreased activity of uroporphyrinogen decarboxylase, the fifth enzyme in heme biosynthesis. The disorder represents the only porphyria that is not exclusively inherited monogenetically. In PCT, at least two different types can be distinguished: acquired/sporadic (type I) PCT, in which the enzymatic deficiency is limited to the liver and inherited/familial (type II) PCT, which is inherited as an autosomal dominant trait with a decrease of enzymatic activity in all tissues. In an effort to characterize the molecular basis of PCT in Chile, we identified eight mutations in 18 previously unclassified PCT families by polymerase chain reaction, heteroduplex analysis, and automated sequencing. To study the role of these mutations in disease causality, in vitro expression of all novel missense mutations was studied. Our results indicate that the frequency of familial PCT in Chile is approximately 50%, thus, to our knowledge, representing the highest incidence of familial PCT reported to date. The data further emphasize the molecular heterogeneity in type II PCT and demonstrate the advantages of molecular genetic techniques as a diagnostic tool and in the detection of clinically asymptomatic mutation carriers.
Assuntos
Porfiria Cutânea Tardia/epidemiologia , Porfiria Cutânea Tardia/genética , Uroporfirinogênio Descarboxilase/genética , Uroporfirinogênio Descarboxilase/metabolismo , Chile/epidemiologia , Análise Mutacional de DNA , Saúde da Família , Mutação da Fase de Leitura , Heterogeneidade Genética , Humanos , Incidência , Mutação de Sentido IncorretoRESUMO
We evaluated the porphyrinogenic ability of ethanol (20% in drinking water) per se, its effect on the development of sporadic porphyria cutanea tarda induced by hexachlorobenzene in female Wistar rats (170-190 g, N = 8/group), and the relationship with hepatic damage. Twenty-five percent of the animals receiving ethanol increased up to 14-, 25-, and 4.5-fold the urinary excretion of delta-aminolevulinate, porphobilinogen, and porphyrins, respectively. Ethanol exacerbated the precursor excretions elicited by hexachlorobenzene. Hepatic porphyrin levels increased by hexachlorobenzene treatment, while this parameter only increased (up to 90-fold) in some of the animals that received ethanol alone. Ethanol reduced the activities of uroporphyrinogen decarboxylase, delta-aminolevulinate dehydrase and ferrochelatase. In the ethanol group, many of the animals showed a 30% decrease in uroporphyrinogen activity; in the ethanol + hexachlorobenzene group, this decrease occurred before the one caused by hexachlorobenzene alone. Ethanol exacerbated the effects of hexachlorobenzene, among others, on the rate-limiting enzyme delta-aminolevulinate synthetase. The plasma activities of enzymes that are markers of hepatic damage were similar in all drug-treated groups. These results indicate that 1) ethanol exacerbates the biochemical manifestation of sporadic hexachlorobenzene-induced porphyria cutanea tarda; 2) ethanol per se affects several enzymatic and excretion parameters of the heme metabolic pathway; 3) since not all the animals were affected to the same extent, ethanol seems to be a porphyrinogenic agent only when there is a predisposition, and 4) hepatic damage showed no correlation with the development of porphyria cutanea tarda.
Assuntos
Etanol/farmacologia , Ferroquelatase/efeitos dos fármacos , Fígado/efeitos dos fármacos , Porfiria Cutânea Tardia/induzido quimicamente , Solventes/farmacologia , Uroporfirinogênio Descarboxilase/efeitos dos fármacos , Animais , Sistema Enzimático do Citocromo P-450/análise , Modelos Animais de Doenças , Feminino , Ferroquelatase/metabolismo , Hexaclorobenzeno , Fígado/enzimologia , Fígado/patologia , Porfobilinogênio/urina , Sintase do Porfobilinogênio/urina , Porfiria Cutânea Tardia/enzimologia , Porfiria Cutânea Tardia/urina , Porfirinas/urina , Ratos , Ratos Wistar , Uroporfirinogênio Descarboxilase/metabolismoRESUMO
We characterized Uroporphyrinogen decarboxylase (UroD) (E.C. 4.1.1.37) in hepatopancreas of the crab Chasmagnathus granulatus as a first step to establish this enzyme as a possible biomarker for environmental contamination. We performed a comparative study of crab UroD with the enzyme UroD present in Wistar rat liver, which is known as a useful indicator of intoxication by polyhalogenated aromatic hydrocarbons (PAHs). The final products were the same in crab and rat UroD: the remaining substrate (8-carboxyl-porphyrinogen), the final product Coproporphyrinogen (4-COOH) and intermediate compounds with 7-, 6- and 5-COOH. The elimination of the second carboxyl group seems to be the rate-limiting step in this multiple decarboxylation, because large amounts of 7-COOH porphyrinogen are accumulated. The V(max)/K(m) ratio was 100-fold higher for rat liver UroD than for crab hepatopancreas UroD, suggesting a higher efficiency of the rat enzyme. Optimum pH for enzyme activity was 7.2 and 6.8 for crab and rat, respectively. Although both systems showed the same optimum temperature (47 degrees C), the activation energy was clearly different, 51.5 kJ/mol for C. granulatus and 5.4 kJ/mol for Rattus norvegicus (Wistar strain). Superdex 75 gel chromatography yielded a single symmetrical peak with an apparent molecular mass of 48+/-3 kDa for crab hepatopancreas UroD, suggesting the existence of only one enzymatic species in C. granulatus.
Assuntos
Decápodes/enzimologia , Sistema Digestório/enzimologia , Uroporfirinogênio Descarboxilase/metabolismo , Animais , Descarboxilação , Poluentes Ambientais/metabolismo , Hidrocarbonetos Halogenados/metabolismo , Concentração de Íons de Hidrogênio , Cinética , Fígado/enzimologia , Porfirinogênios/metabolismo , Ratos , Ratos Wistar , Temperatura , Uroporfirinogênio Descarboxilase/químicaRESUMO
The naturally occurring polyamines--putrescine, spermidine and spermine--are organic cations present in all living cells and essential for cell growth and differentiation. The aim of the present study was to extend the investigations on the effects of porphyrinogenic compounds on polyamine metabolism. This was achieved by studying putrescine, spermidine and spermine levels in a model of acute porphyria, i.e. 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-induced porphyria, and in a model of non-acute porphyria, i.e. hexachlorobenzene (HCB)-induced porphyria. HCB administration to female Wistar rats for 7, 14, 21, 28 and 56 days did not alter polyamine levels in liver, even though rats presented clear signs of HCB-induced porphyria. In contrast to HCB, DDC treatment resulted in a remarkable increase in putrescine levels in the liver of female and male Sprague-Dawley rats. This increase was due, at least in part, to ornithine decarboxylase (ODC) activation. DDC induction of putrescine levels did not show organ specificity, since it could also be seen in adrenal gland. Interestingly, the deregulation of polyamine biosynthesis occurred concomitantly with the deregulation of the heme biosynthetic pathway. In addition to porphyria, it is known that DDC intoxication affects several proteins of the hepatocyte cytoskeleton. It is suggested that DDC-induced increase in ODC activity and putrescine levels may be an early event contributing to alter the cytoskeleton.
Assuntos
Poliaminas Biogênicas/metabolismo , Dicarbetoxi-Di-Hidrocolidina/farmacologia , Hexaclorobenzeno/farmacologia , Porfirinas/biossíntese , 5-Aminolevulinato Sintetase/metabolismo , Animais , Feminino , Ferroquelatase/metabolismo , Fígado/efeitos dos fármacos , Fígado/metabolismo , Masculino , Ornitina Descarboxilase/metabolismo , Proteínas/metabolismo , Ratos , Ratos Sprague-Dawley , Ratos Wistar , Caracteres Sexuais , Uroporfirinogênio Descarboxilase/metabolismoRESUMO
The aims of the present work were: (1) to investigate whether the strong decrease of liver uroporphyrinogen decarboxylase (UroD) activity observed in experimental porphyria cutanea tarda is due to alteration of the enzymatic protein and (2) to improve the knowledge about the normal liver enzyme. With these purposes, several physicochemical studies for enzymatic characterization were carried out comparatively on the 12-fold purified liver enzyme of both normal and hexachlorobenzene porphyric rat. The study shows that the enzyme from porphyric rats has a higher activation energy, lower reactivity index and lower optimum pH than the normal one. In addition, it did not reach the Vmax at any of the substrate concentrations assayed (up to 28 microM uroporphyrinogen III), while the normal enzyme reached the plateau around 14 microM. The porphyric enzyme appears to be more protected than the normal against the inhibitory action of several metals, particularly Cu2+ and Pb2+, and against thermal inactivation. Zn2+ did not affect enzymatic activity, whereas Cu2+, Hg2+, Fe2+, Pb2+, and Cd2+ lowered the activities of both normal and porphyric enzyme in a dose-related way. It was also observed that the larger the atomic radius in its hydrated state, the lower the effect of the metal. Neither glutathione nor dithiothreitol significantly altered enzymatic activity in the range of concentrations assayed. beta-Mercaptoethanol had diverse effects, as regards both the concentration assayed and the enzymatic sample used. Assays with cystine showed a dual behaviour of both normal and porphyric enzymatic activity. Western blots for both preparations revealed a single band (65 kDa) with a similar intensity. This study show that hexachlorobenzene treatment modifies the physicochemical properties of liver UroD leading to a sharp decrease of its activity, without affecting its antigenic reactivity probably as a consequence of changes at the conformational level promoted by the binding of its reported inhibitor.
Assuntos
Fungicidas Industriais/metabolismo , Hexaclorobenzeno/metabolismo , Fígado/enzimologia , Uroporfirinogênio Descarboxilase/metabolismo , Animais , Antígenos/imunologia , Feminino , Fungicidas Industriais/farmacologia , Hexaclorobenzeno/farmacologia , Concentração de Íons de Hidrogênio , Fígado/efeitos dos fármacos , Ratos , Ratos Wistar , TemperaturaRESUMO
The aim of the present study was to determine whether short-term administration of hexachlorobenzene (HCB) (1 g/kg body wt., suspended in water, 5 days/week), could cause and maintain marked porphyria in the absence of the exogenous drug, and whether porphyria parameters can be useful as biomarkers of HCB persistence in rats. Hepatic uroporphyrinogen decarboxylase activity, its inhibitor formation, porphyrin content and composition were studied in Wistar rats treated with the fungicide for 1, 2, 3, or 4 weeks and then withdrawn for a 20-week period. The time course of urinary porphyrin excretion was studied for 7 weeks either by continuous treatment for the entire period, or a 1-week HCB administration. The degree of porphyria achieved by rats after 20 weeks of suspended HCB administration was severe, independent of the length of the treatment, and even higher than that observed in animals analysed immediately at the end of each treatment. Rats treated with HCB for 1 week showed a modest decrease in uroporphyrinogen decarboxylase and low inhibitor formation, and exhibited a greater enzyme inhibition, inhibitor formation, hepatic porphyrin accumulation, and an altered pattern of porphyrin composition in the absence of the exogenous drug. Independent of the treatment, urinary porphyrins rose after a delay of 5 weeks. Substantial amounts of HCB were still found in fat of rats treated with HCB for 1 week, after a withdrawal period of 20 weeks. These results suggest that the high persistence of HCB in tissues acts as a continuous source of the xenobiotic, and stimulus for heme biosynthesis derangement. The alterations induced by HCB within 1 week of treatment could be regarded as an initial trigger for irreversible damage on heme metabolism. Thus, abnormalities in heme biosynthesis can be considered effective markers of HCB persistence in rats or of irreversible HCB-induced damage. Taking into account the delayed and enhanced metabolic effects of HCB, it is advisable that porphyria parameters should be evaluated not only immediately after exposure, but also some time afterwards, especially in susceptible and occupationally-exposed populations.
Assuntos
Fungicidas Industriais/toxicidade , Heme/metabolismo , Hexaclorobenzeno/toxicidade , Porfirias/induzido quimicamente , Tecido Adiposo/efeitos dos fármacos , Tecido Adiposo/metabolismo , Animais , Animais não Endogâmicos , Biomarcadores/análise , Esquema de Medicação , Inibidores Enzimáticos/toxicidade , Feminino , Fungicidas Industriais/administração & dosagem , Fungicidas Industriais/farmacocinética , Hexaclorobenzeno/administração & dosagem , Hexaclorobenzeno/farmacocinética , Fígado/efeitos dos fármacos , Fígado/enzimologia , Porfirias/metabolismo , Ratos , Ratos Wistar , Fatores de Tempo , Uroporfirinogênio Descarboxilase/antagonistas & inibidores , Uroporfirinogênio Descarboxilase/metabolismoRESUMO
In Saccharomyces cerevisiae, as in all eukaryotic organisms, delta-aminolevulinic acid (ALA) is a precursor of porphyrin biosynthesis, a very finely regulated pathway. ALA enters yeast cells through the gamma-aminobutyric acid (GABA) permease Uga4. The incorporation of a metabolite into the cells may be a limiting step for its intracellular metabolization. To determine the relationship between ALA transport and ALA metabolization, ALA incorporation was measured in yeast mutant strains deficient in the delta-aminolevulinic acid-synthase, uroporphyrinogen III decarboxylase, and ferrochelatase, three enzymes involved in porphyrin biosynthesis. Results presented here showed that neither intracellular ALA nor uroporphyrin or protoporphyrin regulates ALA incorporation, indicating that ALA uptake and its subsequent metabolization are not related to each other. Thus a key metabolite as it is, ALA does not have a transport system regulated according to its role.
Assuntos
Ácido Aminolevulínico/metabolismo , Transportadores de Ânions Orgânicos , Porfirinas/biossíntese , Porfirinas/metabolismo , Saccharomyces cerevisiae/metabolismo , 5-Aminolevulinato Sintetase/deficiência , 5-Aminolevulinato Sintetase/genética , 5-Aminolevulinato Sintetase/metabolismo , Ácido Aminolevulínico/farmacologia , Transporte Biológico , Ferroquelatase/genética , Ferroquelatase/metabolismo , Proteínas da Membrana Plasmática de Transporte de GABA , Genes Fúngicos/genética , Cinética , Proteínas de Membrana Transportadoras/metabolismo , Mutação/genética , Porfobilinogênio/metabolismo , Sintase do Porfobilinogênio/metabolismo , Protoporfiria Eritropoética , Protoporfirinas/metabolismo , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/enzimologia , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae , Uroporfirinogênio Descarboxilase/deficiência , Uroporfirinogênio Descarboxilase/genética , Uroporfirinogênio Descarboxilase/metabolismo , Uroporfirinas/metabolismoRESUMO
In the present study, the effects of hexachlorobenzene (HCB) on lipid peroxidation and heme metabolism in the different constitutive suborgans of the kidney were determined. For this purpose, conjugated diene and malondialdehyde levels, as lipid peroxidation parameters, and porphyrin accumulation, uroporphyrinogen decarboxylase activity, and its inhibitor formation, as measures of heme metabolism, were determined in renal cortex, medulla, and papilla. Adult Wistar rats were treated with HCB during 1, 2, 3, or 4 weeks. A significant increase in cortical conjugated dienes was observed from the 1st week of treatment. The malondialdehyde levels rose by 47, 34, and 28% after 2, 3, and 4 weeks of intoxication, respectively. The porphyrin content showed a tenfold increase after 4 weeks of treatment, and the uroporphyrinogen decarboxylase activity was reduced by 26 and 58% with respect to control values after 3 and 4 weeks of treatment, respectively. The results demonstrate a direct correlation between the oxidative environment and the effect elicited by the drug on heme metabolism in the renal cortex. In contrast, in papilla and medulla, where the antioxidant systems were higher, HCB showed no porphyrinogenic effect.
Assuntos
Heme/metabolismo , Hexaclorobenzeno/toxicidade , Rim/citologia , Peroxidação de Lipídeos/efeitos dos fármacos , Porfirias/metabolismo , Animais , Biomarcadores , Inibidores Enzimáticos/farmacologia , Feminino , Rim/efeitos dos fármacos , Córtex Renal/metabolismo , Fígado/metabolismo , Malondialdeído/metabolismo , Porfirias/induzido quimicamente , Porfirinas/metabolismo , Ratos , Ratos Wistar , Uroporfirinogênio Descarboxilase/antagonistas & inibidores , Uroporfirinogênio Descarboxilase/metabolismoRESUMO
Chronic administration of Hexachlorobenzene, with or without the simultaneous administration of Tioctamide was assayed. Hexachlorobenzene alone produced the characteristic porphyria, detected through an increase of the urinary excretion and the hepatic accumulation of porphyrins, as well as by a decrease of the Uroporphyrinogen decarboxylase activity. The content of hepatic conjugated dienes did not change while those of malondialdehyde increased, although without reaching levels of statistical significance. These results would indicate the occurrence of an light lipid peroxidation process. The Thioctamide (25 mg/kg body weight) produced more noxious effects than protective ones, which were detected by a high level of Glutamate piruvate transaminase activity and a decrease of the hepatic Uroporphyrinogen decarboxylase activity, at its first step of decarboxylation. These results might indicate that: 1) high doses of Thioctamide decreases Uroporphyrinogen decarboxylase activity, masking its possible protective effect from Hexachlorobenzene's action through free radicals production and, 2) Uroporphyrinogen decarboxylase is a more sensitive parameter than conjugated dienes or malondialdehyde levels to assay the free radicals in vivo Hexachlorobenzene production. In any case, the Thioctamide assayed in lower and non toxic doses, perhaps might protect against Hexachlorobenzene's action through its free radical scavenger ability.
Assuntos
5-Aminolevulinato Sintetase/urina , Alanina Transaminase/efeitos dos fármacos , Amidas/farmacologia , Fungicidas Industriais/toxicidade , Hexaclorobenzeno/toxicidade , Peroxidação de Lipídeos/efeitos dos fármacos , Fígado/química , Porfobilinogênio/urina , Porfirinas/urina , Ácido Tióctico/farmacologia , Uroporfirinogênio Descarboxilase/metabolismo , Alanina Transaminase/metabolismo , Animais , Radicais Livres/metabolismo , Fígado/enzimologia , Ratos , Ratos Wistar , Fatores de TempoRESUMO
In the last decades several authors have observed a frequent association between diabetes mellitus and porphyria, mainly porphyria cutanea tarda. In previous studies, it has been demonstrated that both d delta d-aminolevulic acid dehydratase (ALA-D) and porphobilinogen deaminase (PBG-D), enzymes of the heme pathway, are inhibited by high concentrations of glucose in vitro in crude preparations of erythrocytes. The activity of these same enzymes was diminished in different tissues obtained from streptozotocin induced diabetic mice. Therefore, we decided to investigate the incidence of heme metabolism alterations in diabetes mellitus in a population of 100 non selected adult patients. The activities of erythrocytic ALA-D and PBG-D were measured. Rhodanese, an enzyme of the sulfocompounds pathway closely related to the regulation of heme biosynthesis, was also studied. Urine porphyrin content as well as the chromatographic pattern of esterified porphyrins were determined. ALA-D and PBG-D activities were diminished in diabetic patients (40 and 20 respectively), while rhodanese was only slightly increased (Fig. 1). ALA-D activity was subnormal in a 92 of the complete diabetic population, while PBG-D activity was less than normal in a 79 of the same population. No significative differences between enzymic activities were observed in the groups insulin and non-insulin dependent (Fig. 3). Urine porphyrin content was increased in 5 of the diabetic population. Chromatographic pattern of urinary porphyrins was notably altered in diabetic patients irrespectively of their porphyrin content (Fig. 4), suggesting an alteration in the enzyme uroporphyrinogen decarboxylase resembling the primary enzymic defect observed in porphyria cutanea tarda.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Diabetes Mellitus , Heme , Glicemia , Diabetes Mellitus , Hidroximetilbilano Sintase , Porfiria Cutânea Tardia/etiologia , Porfirinas , Sintase do Porfobilinogênio/metabolismo , Uroporfirinogênio Descarboxilase/metabolismoRESUMO
In the last decades several authors have observed a frequent association between diabetes mellitus and porphyria, mainly porphyria cutanea tarda. In previous studies, it has been demonstrated that both d delta d-aminolevulic acid dehydratase (ALA-D) and porphobilinogen deaminase (PBG-D), enzymes of the heme pathway, are inhibited by high concentrations of glucose in vitro in crude preparations of erythrocytes. The activity of these same enzymes was diminished in different tissues obtained from streptozotocin induced diabetic mice. Therefore, we decided to investigate the incidence of heme metabolism alterations in diabetes mellitus in a population of 100 non selected adult patients. The activities of erythrocytic ALA-D and PBG-D were measured. Rhodanese, an enzyme of the sulfocompounds pathway closely related to the regulation of heme biosynthesis, was also studied. Urine porphyrin content as well as the chromatographic pattern of esterified porphyrins were determined. ALA-D and PBG-D activities were diminished in diabetic patients (40 and 20 respectively), while rhodanese was only slightly increased (Fig. 1). ALA-D activity was subnormal in a 92 of the complete diabetic population, while PBG-D activity was less than normal in a 79 of the same population. No significative differences between enzymic activities were observed in the groups insulin and non-insulin dependent (Fig. 3). Urine porphyrin content was increased in 5 of the diabetic population. Chromatographic pattern of urinary porphyrins was notably altered in diabetic patients irrespectively of their porphyrin content (Fig. 4), suggesting an alteration in the enzyme uroporphyrinogen decarboxylase resembling the primary enzymic defect observed in porphyria cutanea tarda.(ABSTRACT TRUNCATED AT 250 WORDS)(Au)
Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , RESEARCH SUPPORT, NON-U.S. GOVT , Diabetes Mellitus/metabolismo , Heme/metabolismo , Glicemia/análise , Diabetes Mellitus/complicações , Diabetes Mellitus/enzimologia , Hidroximetilbilano Sintase/metabolismo , Sintase do Porfobilinogênio/metabolismo , Porfiria Cutânea Tardia/etiologia , Porfirinas/urina , Uroporfirinogênio Descarboxilase/metabolismoRESUMO
In the last decades several authors have observed a frequent association between diabetes mellitus and porphyria, mainly porphyria cutanea tarda. In previous studies, it has been demonstrated that both d delta d-aminolevulic acid dehydratase (ALA-D) and porphobilinogen deaminase (PBG-D), enzymes of the heme pathway, are inhibited by high concentrations of glucose in vitro in crude preparations of erythrocytes. The activity of these same enzymes was diminished in different tissues obtained from streptozotocin induced diabetic mice. Therefore, we decided to investigate the incidence of heme metabolism alterations in diabetes mellitus in a population of 100 non selected adult patients. The activities of erythrocytic ALA-D and PBG-D were measured. Rhodanese, an enzyme of the sulfocompounds pathway closely related to the regulation of heme biosynthesis, was also studied. Urine porphyrin content as well as the chromatographic pattern of esterified porphyrins were determined. ALA-D and PBG-D activities were diminished in diabetic patients (40% and 20% respectively), while rhodanese was only slightly increased (Fig. 1). ALA-D activity was subnormal in a 92% of the complete diabetic population, while PBG-D activity was less than normal in a 79% of the same population. No significative differences between enzymic activities were observed in the groups insulin and non-insulin dependent (Fig. 3). Urine porphyrin content was increased in 5% of the diabetic population. Chromatographic pattern of urinary porphyrins was notably altered in diabetic patients irrespectively of their porphyrin content (Fig. 4), suggesting an alteration in the enzyme uroporphyrinogen decarboxylase resembling the primary enzymic defect observed in porphyria cutanea tarda.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Diabetes Mellitus/metabolismo , Heme/metabolismo , Adulto , Glicemia/análise , Complicações do Diabetes , Diabetes Mellitus/enzimologia , Feminino , Humanos , Hidroximetilbilano Sintase/metabolismo , Masculino , Pessoa de Meia-Idade , Sintase do Porfobilinogênio/metabolismo , Porfiria Cutânea Tardia/etiologia , Porfirinas/urina , Uroporfirinogênio Descarboxilase/metabolismoRESUMO
1. A detailed study of the urinary excretion pattern of porphyrins in humans chronically exposed to As via drinking water was performed using high performance liquid chromatography (HPLC) 2. Thirty-six individuals (15 men and 21 women) were selected from a town which had 0.400 mg L-1 of As in drinking water. The control group consisted of thirty-one individuals (13 men and 18 women) whose As concentration in drinking water was 0.020 mg L-1. 3. The major abnormalities in the urinary porphyrin excretion pattern observed in arsenic-exposed individuals were: (a) significant reductions in coproporphyrin III excretion resulting in decreases in the COPRO III/COPRO I ratio, and (b) significant increases in uroporphyrin excretion. Both alterations were responsible for the decrease in the COPRO/URO ratio. 4. No porphyrinogenic response was found in individuals with urinary As concentrations below 1,000 micrograms of As g-1 of creatinine. However, as arsenic concentrations exceeded this value, the excretion of porphyrins (except coproporphyrin III) increased proportionally. 5. The prevalence of clinical signs of arsenicism showed a direct relationship to both As concentration in urine and time-weighted exposure to As. A direct relationship between time-weighted exposure and alterations in urinary porphyrin excretion ratios was also observed. 6. The alterations found are compatible with a lower uroporphyrinogen decarboxylase activity in arsenic-exposed individuals. However, the similarities in the urinary porphyrin excretion pattern between As-exposed individuals and Dubin-Johnson syndrome patients suggest that impairments in the excretion of coproporphyrin isomers may also contribute to the pattern observed.
Assuntos
Intoxicação por Arsênico , Coproporfirinas/urina , Uroporfirinas/urina , Poluentes Químicos da Água/intoxicação , Adulto , Idoso , Arsênio/urina , Cromatografia Líquida de Alta Pressão , Creatinina/urina , Ingestão de Líquidos , Feminino , Humanos , Icterícia Idiopática Crônica/metabolismo , Masculino , México , Pessoa de Meia-Idade , Análise de Regressão , Uroporfirinogênio Descarboxilase/metabolismo , Poluentes Químicos da Água/urinaRESUMO
1. URO-D was investigated in crude extracts from mouse mammary carcinoma, normal mouse (NM) liver and tumor-bearing mouse (TBM) liver. 2. URO-D from TBM liver and tumor appears to be more sensitive to increasing concentrations of UROgen than the NM liver enzyme. 3. In tumor the rate-limiting step seems to be the decarboxylation of the first carboxyl group, but this was not so clear for the NM and the TBM liver URO-D. 4. URO-D activity was enhanced when incubated at higher temperatures in the presence of its substrate, suggesting that UROgen might afford some protection of the enzyme against heat inactivation. 5. The optimum pH for all three sources is around 7.0.
Assuntos
Neoplasias Mamárias Experimentais/enzimologia , Uroporfirinogênio Descarboxilase/metabolismo , Animais , Concentração de Íons de Hidrogênio , Cinética , Fígado/enzimologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Especificidade por Substrato , Temperatura , UroporfirinogêniosRESUMO
Se llevaron a cabo estudios para elucidar si en la porfiria por hexaclorobenceno (HCB) están alterados los contenidos de hierro total, no hémico en hígado y si existe alguna relación entre estas alteraciones y el decrenento de la porfirinógeno carboxi-liasa (PCL) hepática en ratas tratadas con la droga. Se observó que en los hígados porfíricos los niveles de hierro total y no hémico incrementaron significativamente como consecuencia de la intoxicación por HCB, mientras que este tratamiento produjo un decremento no significativo en el contenido de hierro hémico. Preparaciones enzimáticas de hígados porfíricos filtradas a través de columnas de Sephadex G-25, que separan el hierro libre y que tienen un contenido de hierro-proteína mayor que las normales, exhibieron una fuerte inhibición de PCL. Agentes quelantes, alfa alfa' bipiridilo y 8-hidroxiquinolina, no revierten tal inhibición. Se ensayó también el efecto in vitro de diferentes concentraciones de hierro inogánico, ferritina y hemina sobre la actividad de PCL normal. Así se observó que hierro inogánico y hemina producen ligera inhibición de PCL cuando se añaden en concentraciones mayores que las correspondientes a un hígado porfírico (0.08 mM y 10-6 M respectivamente como promedio en el medio de incubación). Por lo tanto dichas inhibiciones no tienen significado fisiológico. La ferritina no modifica el proceso de descarboxilación. De estos resultados surge que el hierro no desempeña un papel directo en el decremento de la actividad PCL en la porfiria experimental por HCB, no siendo el inhibidor que se pone de manifiesto en los ensayos de calentamiento. El hierro podría quizás estimular la metabolización del HCB dando origen a metabolitos activos
Assuntos
Ratos , Animais , Feminino , Hexaclorobenzeno/farmacologia , Ferro/metabolismo , Hepatopatias/induzido quimicamente , Porfirias/induzido quimicamente , Uroporfirinogênio Descarboxilase/metabolismo , Modelos Animais de Doenças , Fígado/metabolismo , Heme/metabolismoRESUMO
Se llevaron a cabo estudios para elucidar si en la porfiria por hexaclorobenceno (HCB) están alterados los contenidos de hierro total, no hémico en hígado y si existe alguna relación entre estas alteraciones y el decrenento de la porfirinógeno carboxi-liasa (PCL) hepática en ratas tratadas con la droga. Se observó que en los hígados porfíricos los niveles de hierro total y no hémico incrementaron significativamente como consecuencia de la intoxicación por HCB, mientras que este tratamiento produjo un decremento no significativo en el contenido de hierro hémico. Preparaciones enzimáticas de hígados porfíricos filtradas a través de columnas de Sephadex G-25, que separan el hierro libre y que tienen un contenido de hierro-proteína mayor que las normales, exhibieron una fuerte inhibición de PCL. Agentes quelantes, alfa alfa bipiridilo y 8-hidroxiquinolina, no revierten tal inhibición. Se ensayó también el efecto in vitro de diferentes concentraciones de hierro inogánico, ferritina y hemina sobre la actividad de PCL normal. Así se observó que hierro inogánico y hemina producen ligera inhibición de PCL cuando se añaden en concentraciones mayores que las correspondientes a un hígado porfírico (0.08 mM y 10-6 M respectivamente como promedio en el medio de incubación). Por lo tanto dichas inhibiciones no tienen significado fisiológico. La ferritina no modifica el proceso de descarboxilación. De estos resultados surge que el hierro no desempeña un papel directo en el decremento de la actividad PCL en la porfiria experimental por HCB, no siendo el inhibidor que se pone de manifiesto en los ensayos de calentamiento. El hierro podría quizás estimular la metabolización del HCB dando origen a metabolitos activos (AU)
Assuntos
Ratos , Animais , Feminino , Ferro/metabolismo , Hepatopatias/induzido quimicamente , Hexaclorobenzeno/farmacologia , Porfirias/induzido quimicamente , Uroporfirinogênio Descarboxilase/metabolismo , Fígado/metabolismo , Heme/metabolismo , Modelos Animais de DoençasRESUMO
Studies were carried out to elucidate if in the hexachlorobenzene (HCB) porphyria, total, nonhaem and haem iron contents in liver are altered and if any relation exists between these alterations and the hepatic porphyrinogen carboxy-lyase (PCL) decrease in rats treated with the drug. It was observed that in porphyric livers total and non-haem iron levels increased significantly as a consequence of HCB intoxication while this treatment produced a non significant decrease in the haem iron content. Enzymic preparations of porphyric livers filtered through Sephadex G-25 columns which separate the free iron and that has a content of iron-protein greater than those in normals, exhibited a strong inhibition of PCL. Chelating agents, alpha' alpha' bipyridyl and 8-hydroxyquinoline do not revert such inhibition. The effect in vitro of ferritin, haemin and inorganic iron at different concentrations on normal PCL activity was also assayed. So, it could be observed that inorganic iron and haemin produce slight inhibition of PCL when added in concentrations higher than those corresponding to a porphyric liver (0.08 mM and 10(-6) M, respectively, as mean in the incubation media). So, they have not physiological significance. Ferritin does not modify the decarboxylation process. From these results it arises that iron does not play a direct role in the decrease of PCL activity in the experimental porphyria by HCB, not being the inhibitor made evident by heating assays. Iron could perhaps stimulate the metabolization of HCB, giving rise to active metabolite.