RESUMO
The purpose of this study was to examine the changes of cellular cholesterol efflux from macrophages in patients with type II diabetes mellitus (DM), and to determine the expression of CYP7A1, ABCG5, and LXRß therein. We recruited 30 patients with type II DM (including 15 patients complicated with coronary heart disease and 15 patients with DM only) and 15 normal controls for this study. Peripheral blood monocytes were isolated for macrophage culture. The mRNA and protein expression levels of CYP7A1, ABCG5, and LXRß were determined using real-time polymerase chain reaction and western blot. The macrophage cholesterol efflux rate was determined with 10% autoserum and standard serum as receptors. We determined that the expression levels of macrophage CYP7A1 mRNA and protein in the type II DM group were significantly lower than those in the control group, but no differences were found in the ABCG5 and LXRß expression levels between the groups. The macrophage cholesterol efflux rate in the patients with type II DM was also significantly decreased compared with that of the normal control subjects (P < 0.01). Furthermore, CYP7A1 mRNA expression and macrophage cholesterol efflux rate were significantly positively correlated. In summary, this study demonstrated that the macrophage cholesterol efflux in patients with type II DM was significantly reduced, and that this reduction was associated with the down-regulation of CYP7A1 expression.
Assuntos
Colesterol 7-alfa-Hidroxilase/genética , Colesterol/metabolismo , Doença das Coronárias/enzimologia , Diabetes Mellitus Tipo 2/enzimologia , Macrófagos/enzimologia , Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Transportadores de Cassetes de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/metabolismo , Adulto , Estudos de Casos e Controles , Células Cultivadas , Colesterol/sangue , Colesterol 7-alfa-Hidroxilase/metabolismo , Doença das Coronárias/sangue , Doença das Coronárias/etiologia , Diabetes Mellitus Tipo 2/sangue , Diabetes Mellitus Tipo 2/complicações , Regulação para Baixo , Repressão Enzimática , Feminino , Humanos , Lipoproteínas/genética , Lipoproteínas/metabolismo , Receptores X do Fígado , Macrófagos/metabolismo , Masculino , Pessoa de Meia-Idade , Receptores Nucleares Órfãos/genética , Receptores Nucleares Órfãos/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismoRESUMO
In the classical model of edema formation and hyperalgesia induced by carrageenan administration in rat paw, the increase in prostaglandin E2 (PGE2) production in the central nervous system (CNS) contributes to the severity of the inflammatory and pain responses. Prostaglandins are generated by the cyclooxygenase (COX). There are two distinct COX isoforms, COX-1 and COX-2. In inflammatory tissues, COX-2 is greatly expressed producing proinflammatory prostaglandins (PGs). Low-level laser therapy (LLLT) has been used in the treatment of inflammatory pathologies, reducing both pain and acute inflammatory process. Herein we studied the effect of LLLT on both COX-2 and COX-1 messenger RNA (mRNA) expression in either subplantar or brain tissues taken from rats treated with carrageenan. The experiment was designed as follows: A1 (saline), A2 (carrageenan-0.5 mg/paw), A3 (carrageenan-0.5 mg/paw + LLLT), A4 (carrageenan-1.0 mg/paw), and A5 (carrageenan-1.0 mg/paw + LLLT). Animals from the A3 and A5 groups were irradiated at 1 h after carrageenan administration, using a diode laser with an output power of 30 mW and a wavelength of 660 nm. The laser beam covered an area of 0.785 cm(2), resulting in an energy dosage of 7.5 J/cm(2). Both COX-2 and COX-1 mRNAs were measured by RT-PCR. Six hours after carrageenan administration, COX-2 mRNA expression was significantly increased both in the subplantar (2.2-4.1-fold) and total brain (8.65-13.79-fold) tissues. COX-1 mRNA expression was not changed. LLLT (7.5 J/cm(2)) reduced significantly the COX-2 mRNA expression both in the subplantar (~2.5-fold) and brain (4.84-9.67-fold) tissues. The results show that LLLT is able to reduce COX-2 mRNA expression. It is possible that the mechanism of LLLT decreasing hyperalgesia is also related to its effect in reducing the COX-2 expression in the CNS.
Assuntos
Encéfalo/enzimologia , Lasers Semicondutores/uso terapêutico , Terapia com Luz de Baixa Intensidade , Animais , Encéfalo/imunologia , Carragenina/farmacologia , Ciclo-Oxigenase 1/genética , Ciclo-Oxigenase 1/metabolismo , Ciclo-Oxigenase 2/genética , Ciclo-Oxigenase 2/metabolismo , Dinoprostona/biossíntese , Edema/enzimologia , Edema/radioterapia , Repressão Enzimática/imunologia , Repressão Enzimática/efeitos da radiação , Hiperalgesia/radioterapia , Inflamação/enzimologia , Inflamação/radioterapia , Masculino , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos WistarRESUMO
The molecular and biochemical effects of an insecticidal toxin extracted from Meloidae beetles were investigated on Helicoverpa armigera. The toxin was identified as cantharidin, a well-known natural compound produced by beetles of family Meloidae and Oedemeridae. Furthermore, the effect of the toxin on the metabolic enzymes alkaline phosphatase (ALP) and glutathione S-transferase (GST), responsible for the metabolism of insecticides, was also investigated. Results of a diet incorporation bioassay performed under laboratory conditions showed that the LC50 value of cantharidin was 0.068 mg/g. The body weight of the insect was also significantly reduced by cantharidin treatment. The LC10 concentration of cantharidin, 0.01 mg/g, was also tested to determine its effect on ALP and GST. Our results showed that cantharidin significantly inhibited ALP activity after 48 h, whereas GST activity was significantly inhibited after 24 h. The decline of ALP and GST transcript levels was also validated by semiquantitative RT-PCR analysis. It may be concluded from the results that ALPs and GSTs may be targets of the cantharidin intoxication mechanism. Moreover, the inability of ALP and GST to metabolize cantharidin shows that the mechanism of detoxification for cantharidin is different from that for conventional insecticides. On the basis of our investigations, the chemical structure of insecticides may be modified using a model structure of cantharidin, to avoid metabolism by metabolic enzymes.
Assuntos
Cantaridina/farmacologia , Besouros/química , Inseticidas/farmacologia , Mariposas/efeitos dos fármacos , Fosfatase Alcalina/antagonistas & inibidores , Fosfatase Alcalina/química , Fosfatase Alcalina/genética , Fosfatase Alcalina/metabolismo , Animais , Cantaridina/química , Clonagem Molecular , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Repressão Enzimática , Glutationa Transferase/antagonistas & inibidores , Glutationa Transferase/química , Glutationa Transferase/genética , Glutationa Transferase/metabolismo , Proteínas de Insetos/antagonistas & inibidores , Proteínas de Insetos/química , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Inseticidas/química , Larva/efeitos dos fármacos , Larva/enzimologia , Larva/crescimento & desenvolvimento , Dose Letal Mediana , Mariposas/enzimologia , Mariposas/crescimento & desenvolvimento , Análise de Sequência de DNARESUMO
Cardiovascular diseases involve critical mechanisms including impaired nitric oxide (NO) levels and abnormal matrix metalloproteinase (MMP) activity. While NO downregulates MMP expression in some cell types, no previous study has examined whether NO downregulates MMP levels in endothelial cells. We hypothesized that NO donors could attenuate MMP-9 production by human umbilical vein endothelial cells (HUVECs) as a result of less NFκB activation or cyclic GMP (cGMP)-mediated mechanisms. We studied the effects of DetaNONOate (10-400 µM) or SNAP (50-400 µM) on phorbol 12-myristate 13-acetate (PMA; 10 nM)-induced increases in MMP-9 activity (by gel zymography) or concentrations (by ELISA) as well as on a tissue inhibitor of MMPs' (TIMP)-1 concentrations (by ELISA) in the conditioned medium of HUVECs incubated for 24 h with these drugs. We also examined whether the irreversible inhibitor of soluble guanylyl cyclase ODQ modified the effects of SNAP or whether 8-bromo-cGMP (a cell-permeable analog of cGMP) influenced PMA-induced effects on MMP-9 expression. Total and phospho-NFκB p65 concentrations were measured in HUVEC lysates to assess NFκB activation. Both NO donors attenuated PMA-induced increases in MMP-9 activity and concentrations without significantly affecting TIMP-1 concentrations. This effect was not modified by ODQ, and 8-bromo-cGMP did not affect MMP-9 concentrations. While PMA increased phospho-NFκB p65 concentrations, SNAP had no influence on this effect. In conclusion, this study shows that NO donors may attenuate imbalanced MMP expression and activity in endothelial cells independent of cGMP- or NFκB-mediated mechanisms. Our results may offer an important pharmacological strategy to approach cardiovascular diseases.
Assuntos
GMP Cíclico/fisiologia , Células Endoteliais da Veia Umbilical Humana/enzimologia , Metaloproteinase 9 da Matriz/metabolismo , Óxido Nítrico/fisiologia , Fator de Transcrição RelA/metabolismo , Células Cultivadas , Meios de Cultivo Condicionados , Repressão Enzimática/efeitos dos fármacos , Expressão Gênica , Humanos , Metaloproteinase 9 da Matriz/genética , Óxido Nítrico/farmacologia , Doadores de Óxido Nítrico/farmacologia , Nitrilas/farmacologia , Compostos Nitrosos/farmacologia , Fosforilação , Processamento de Proteína Pós-Traducional , Sulfonas/farmacologia , Acetato de Tetradecanoilforbol/farmacologia , Inibidor Tecidual de Metaloproteinase-1/genética , Inibidor Tecidual de Metaloproteinase-1/metabolismo , Fator de Transcrição RelA/antagonistas & inibidores , Transcrição GênicaRESUMO
The efficacy of conjugated linoleic acid (CLA) in diet supplements for milk fat reduction is well documented in several species. However, the mechanisms by which fatty acids regulate mammary lipogenesis remain largely unknown, especially with regard to gene expression of enzyme and regulators. In this study, 8 Holstein dairy cows in their mid-lactation period were randomly divided into 2 groups. Control cows received a Ca salt of palm oil fatty acid dietary supplement, and those in the CLA group were fed Ca salts of CLA (Ca-CLA), all in a dose of approximately 200 gâcow(-1)âday(-1) for 14 days. The milk yield was recorded daily, and protein, lactose, and fat in the milk were quantified every 3 days for 2 weeks. Fatty acids in the milk were analyzed with gas-liquid chromatography. Measurement of messenger RNA levels of the main lipogenic genes of lipoprotein lipase, acetyl-coenzyme A (CoA) carboxylase, fatty acid synthase, stearoyl-CoA desaturase, and transcription factors such as sterol response element binding protein 1 (SREBP1) and peroxisome proliferator-activated receptor γ was performed in biopsy samples of mammary tissue on the last day. The results indicated that dietary Ca-CLA caused a continuous reduction of milk fat (P < 0.01) with no effect on milk yield, milk protein, and lactose. The fatty acid profile in the milk from the CLA group differed from that from controls, and the yield of milk fatty acid decreased (P < 0.01) with Ca-CLA supplementation. The depressed expression of lipogenic genes (lipoprotein lipase, acetyl-CoA carboxylase, fatty acid synthase, and stearoyl-CoA desaturase) demonstrated inhibition of fatty acid de novo synthesis and uptake in the mammary gland of the CLA group. Furthermore, the gene expression of transcription factor SREBP1 was also downregulated (P < 0.01), but peroxisome proliferator-activated receptor γ was unchanged, suggesting that SREBP1 may play a key role in the regulation of lipogenic gene expression in the lactating mammary gland.
Assuntos
Bovinos/fisiologia , Ácidos Linoleicos Conjugados/administração & dosagem , Lipogênese/genética , Glândulas Mamárias Animais/metabolismo , Leite/metabolismo , Acetil-CoA Carboxilase/genética , Acetil-CoA Carboxilase/metabolismo , Animais , Suplementos Nutricionais , Repressão Enzimática , Ácido Graxo Sintases/genética , Ácido Graxo Sintases/metabolismo , Ácidos Graxos/metabolismo , Feminino , Expressão Gênica , Lactação , Estearoil-CoA Dessaturase/genética , Estearoil-CoA Dessaturase/metabolismoRESUMO
This article describes a simple and robust laboratory exercise on the regulation of membrane unsaturated fatty acid composition in bacteria by a decrease in growth temperature. We take advantage of the well characterized Des pathway of Bacillus subtilis, composed of a Δ5-desaturase (encoded by the des gene) and the canonical two-component system DesK-DesR, to study the transcriptional regulation of des during cold shock. Students analyze the expression of a reporter transcriptional fusion between the des promoter and the bacterial lacZ gene in a wild-type B. subtilis strain and in des or desK-desR mutants grown under different culture conditions. Measurements of ß-galactosidase activity allow them to investigate how the Des pathway works and to assess the role of each component of this regulatory system.
Assuntos
Bacillus subtilis/metabolismo , Membrana Celular/metabolismo , Ácidos Graxos Insaturados/metabolismo , Fluidez de Membrana , Bacillus subtilis/genética , Bacillus subtilis/crescimento & desenvolvimento , Meios de Cultura/química , Dessaturase de Ácido Graxo Delta-5 , Repressão Enzimática , Ácidos Graxos Dessaturases/genética , Ácidos Graxos Dessaturases/metabolismo , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos , Regiões Promotoras Genéticas , Temperatura , Transcrição Gênica , beta-Galactosidase/metabolismoRESUMO
Malathion is an organophosphate (OP) pesticide whose toxicity depends on its bioactivation to malaoxon. Human malathion poisoning has been treated with oximes (mainly pralidoxime) in an attempt to reactivate OP-inhibited acetylcholinesterase (AChE). However, pralidoxime has shown unsatisfactory therapeutic effects in malathion poisoning and its routine use has been questioned. In this study, we evaluated the in vitro potency of standards and newly developed oximes in reactivating malaoxon-inhibited AChE derived from mouse brain supernatants. Malaoxon displayed a concentration-dependent inhibitory effect on mouse brain AChE (IC(50) = 2.36 microM), and pralidoxime caused a modest reactivating effect (30% of reactivation at 600 microM). Obidoxime and trimedoxime, as well as K047 and K075, displayed higher reactivating effects (from 55% to 70% of reactivation at 600 muM) when compared with pralidoxime. The results show that obidoxime, trimedoxime, K074 and K075 present higher reactivating effects on malaoxon-inhibited AChE under in vitro conditions when compared with pralidoxime. Taking into account the unsatisfactory effects of pralidoxime as antidotal treatment in malathion poisonings, the present results suggest that obidoxime, trimedoxime, K074 and K075 might be interesting therapeutic strategies to reactivate malaoxon-inhibited AChE in malathion poisonings.
Assuntos
Antídotos/farmacologia , Encéfalo/efeitos dos fármacos , Inibidores da Colinesterase/toxicidade , Reativadores da Colinesterase/farmacologia , Inseticidas/toxicidade , Malation/análogos & derivados , Oximas/farmacologia , Acetilcolinesterase/metabolismo , Animais , Encéfalo/enzimologia , Butanos/farmacologia , Repressão Enzimática/efeitos dos fármacos , Malation/toxicidade , Masculino , Camundongos , Cloreto de Obidoxima/farmacologia , Compostos de Pralidoxima/farmacologia , Compostos de Piridínio/farmacologia , Trimedoxima/farmacologiaRESUMO
Host invasion by pathogens is frequently associated with the activation of nuclear factor kappaB (NF-kappaB), which modulates the expression of genes involved in the immunological response of the host. However, pathogens may also subvert these mechanisms to secure their survival. We describe the effect of Leishmania amazonensis infection on NF-kappaB transcriptional factor activation in macrophages and the subsequent reduction in inducible nitric oxide synthase (iNOS) expression. L. amazonensis promastigote infection activates the p50/p50 NF-kappaB complex, a classic transcriptional repressor. Interestingly, L. amazonensis promotes the change of the classical p65/p50 NF-kappaB dimer induced by LPS, leading to the p50/p50 NF-kappaB complex activation in macrophages stimulated with LPS. Moreover, this parasite promotes the reduction of p65 total levels in infected macrophages. All these effects contribute to the observation that this parasite is able to restrain the NF-kappaB-dependent transcriptional activity induced by LPS. Strikingly, L. amazonensis reduces the mRNA levels of the iNOS in addition to protein expression and the production of nitric oxide in LPS-stimulated macrophages. Accordingly, as revealed by reporter-gene assays, L. amazonensis-induced iNOS repression requires NF-kappaB sites in the iNOS promoter region. In summary, our results suggest that L. amazonensis has developed an adaptive strategy to escape from host defense by activating the NF-kappaB repressor complex p50/p50. The activation of this specific host transcriptional response negatively regulates the expression of iNOS, favoring the establishment and success of L. amazonensis infection.
Assuntos
Leishmania/imunologia , Leishmaniose/imunologia , Macrófagos/metabolismo , Subunidade p50 de NF-kappa B/metabolismo , Óxido Nítrico Sintase Tipo II/metabolismo , Animais , Linhagem Celular , Repressão Enzimática , Interações Hospedeiro-Patógeno , Humanos , Leishmania/patogenicidade , Leishmaniose/enzimologia , Leishmaniose/genética , Macrófagos/imunologia , Macrófagos/microbiologia , Macrófagos/patologia , Camundongos , Subunidade p50 de NF-kappa B/genética , Óxido Nítrico Sintase Tipo II/genética , Óxido Nítrico Sintase Tipo II/imunologia , Ativação TranscricionalRESUMO
Retamycin is an anthracyclinic antitumoral complex produced by Streptomyces olindensis ICB20. In this work the influence of different glucose concentrations in the feed medium on the production of retamycin was studied. Chemostat cultures employing glucose concentration varying between 10 g/L and 25 g/L showed that use of high glucose concentration resulted in catabolite repression of the biosynthesis of the antitumoral. The highest specific retamycin production rate, qRTM = 7.8 mg/g.h, was obtained when glucose concentration was 10 g/L. The lowest value of qRTM, 2.5 mg/g.h, was observed when glucose concentration was 20 and 25 g/L. The residual glucose concentration varied from 0 to 13 g/L, as the glucose concentration in the feed was increased from 10 to 25 g/L.
A retamicina é um complexo antitumoral antraciclínico produzido por Streptomyces olindensis ICB20. Neste trabalho estudou-se a influência de diferentes concentrações de glicose no meio de alimentação sobre a produção de retamicina. Os resultados de cultivos contínuos mostraram que o uso de elevadas concentrações de glicose resultou em repressão catabólica da biossíntese do antitumoral. A maior velocidade específica de produção de retamicina, qRTM = 7,8 mg/g.h, foi obtida quando a concentração de glicose foi de 10 g/L. O menor valor de qRTM, 2,5 mg/g.h, foi observado quando a concentração de glicose foi de 20 e 25 g/L. A concentração de glicose residual aumentou de 0 a 13 g/L conforme a concentração de glicose na alimentação foi incrementada de 10 a 25 g/L.
Assuntos
Antraciclinas , Ensaios Enzimáticos Clínicos , Técnicas In Vitro , Streptomyces , Meios de Cultura , Repressão Enzimática , Métodos , Estudos de AmostragemRESUMO
Because Rhizobium etli CE3 is normally dependent on an external source of biotin and lacks orthodox biotin biosynthesis genes, we undertook an analysis of biotin uptake in this organism. By complementation of a Sinorhizobium meliloti bioM mutant we isolated an R. etli chromosomal region encoding homologs of the S. meliloti bioMNB genes, whose products have been implicated in intracellular biotin retention in that organism. Disruption of the R. etli bioM resulted in a mutant which took up biotin at a lower rate and accumulated significantly less biotin than the wild type. As in S. meliloti, the R. etli bioMN gene-products resemble the ATPase and permease components, respectively, of an ABC-type transporter. The bioB gene product is in fact similar to members of the BioY family, which has been postulated to function in biotin transport, and we refer to this gene as bioY. An R. etli bioY mutant exhibited lower biotin uptake than the wild-type, providing the first experimental evidence for a role of BioY in biotin transport. We show that the bioMNY operon is transcriptionally repressed by biotin. An analysis of the competitiveness of the wild-type strain versus the bioM mutant showed that the mutant had a diminished capacity to form nodules on bean plants.
Assuntos
Biotina/metabolismo , Óperon , Rhizobium etli/genética , Rhizobium etli/metabolismo , Adenosina Trifosfatases/genética , Clonagem Molecular , DNA Bacteriano , Repressão Enzimática , Regulação Bacteriana da Expressão Gênica , Teste de Complementação Genética , Proteínas de Membrana Transportadoras/genética , Dados de Sequência Molecular , Fixação de Nitrogênio , Transporte Proteico , Análise de Sequência de DNA , Sinorhizobium meliloti/genética , Simportadores/genéticaRESUMO
For a long time, fungi have been characterized by their ability to secrete enzymes, mostly hydrolytic in function, and thus are defined as extracellular degraders. Chitin and chitinolytic enzymes are gaining importance for their biotechnological applications. Particularly, chitinases are used in agriculture to control plant pathogens. Metarhizium anisopliae produces an extracellular chitinase when grown on a medium containing chitin, indicating that synthesis is subject to induction by the substrate. Various sugar combinations were investigated for induction and repression of chitinase. N-acetylglucosamine (GlcNAc) shows a special dual regulation on chitinase production. M. anisopliae has at least two distinct, cell-bound, chitinolytic enzymes when cultured with GlcNAc as one of the carbon sources, and we suggest that this carbohydrate has an important role in protein secretion.
Assuntos
Acetilglucosamina/metabolismo , Quitinases/metabolismo , Hypocreales/enzimologia , Hypocreales/metabolismo , Quitina/metabolismo , Quitinases/biossíntese , Eletroforese em Gel de Poliacrilamida , Indução Enzimática , Repressão Enzimática , Proteínas Fúngicas/biossíntese , Proteínas Fúngicas/metabolismo , Glucose/metabolismo , Fungos Mitospóricos/enzimologia , Fungos Mitospóricos/metabolismoRESUMO
Glutamato desidrogenase dependente de NADP+ (NADP+-Gdh) constitui o primeiro passo enzimático no mecanismo de assimilacão de nitrogênio em Saccharomyces cerevisiae e o conhecimento de sua regulacão é chave na iniciativa de vários propósitos biotecnológicos, tais como a producão de proteína microbiana. A regulacão da atividade NADP+-Gdh em células de Kluyveromyces marxianus foi avaliada a partir de diferentes condicões de suprimento de amonia em cultivo em batelada. Os resultados mostraram que a atividade NADP+-Gdh de K. marxianus foi induzida em uma estreita faixa de concentracão de amonia no meio, sendo reprimida tanto por altas concentracões deste composto quanto pelo produto glutamato. Esta atividade não está associada ao crescimento celular e deve funcionar principalmente no rastreamento de pequenas quantidades de amonia após a parada do crescimento celular. Isto demonstra que NADP+-Gdh não deve ser a principal enzima de assimilacão de amonia em K. marxianus, como tem sido postulado para K. lactis, contudo deve estar submetida ao mesmo mecanismo regulatório encontrado em S. cerevisiae.
Assuntos
Amônia/análise , Ensaios Enzimáticos Clínicos , Desidrogenase de Glutamato (NADP+) , Técnicas In Vitro , Kluyveromyces , Saccharomyces cerevisiae , Aculturação , Repressão EnzimáticaRESUMO
Hansenula polymorpha is a methylotrophic yeast widely employed in biotechnology as a ''protein factory''. Most promoters used for heterologous protein expression, like MOX (methanol oxidase) and DAS (di-hydroxy acetone synthase), are involved in the peroxisomal methanol metabolism (C1 metabolism) and are under strong glucose repression. Interestingly, the MOX promoter is subjected to glucose regulation also in Saccharomyces cerevisiae, a non-methylotrophic yeast in which this phenomenon is well studied. In this species, the transcription factor Tup1p plays an essential role in glucose repression of several genes. This effect is counteracted by the activator Snf1p when glucose is exhausted from medium. Therefore, to test whether this regulatory circuit has been conserved in H. polymorpha, HpTUP1 and HpSNF1 were partially cloned and disrupted. Deletion of HpTUP1 did not affect glucose repression of the major C1 metabolism genes (MOX, DAS). Thus, though conserved, HpTUP1 does not seem to take part in a general glucose repression in H. polymorpha. In contrast, the deletion of HpSNF1 led to significant decreases in the activation of these genes in the absence of glucose. Therefore, the effect of HpSNF1 in transcriptional activation may be through an HpTUP1- independent circuit.
Assuntos
Glucose , Leveduras , Repressão Enzimática , MetanolRESUMO
In this work, we show that the expression of the asnA and asnC genes is regulated by the availability of ammonium in the growth medium. Our results suggest that, under nitrogen-limiting growth conditions, the nitrogen assimilation control (Nac) protein is involved in the repression of the asnC gene, whose product is required to activate the transcription of asnA. We also show that asparagine negatively affects the expression of asnA, independently of the presence of Nac. These results allow us to conclude that asnA transcription is regulated by two different mechanisms that respond to different effectors: nitrogen and asparagine availability.
Assuntos
Aspartato-Amônia Ligase/genética , Proteínas de Bactérias , Carbono-Nitrogênio Ligases com Glutamina como Doadora de N-Amida/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas de Escherichia coli , Escherichia coli/genética , Fatores de Transcrição/metabolismo , Asparagina/metabolismo , Repressão Enzimática , Escherichia coli/enzimologia , Regulação Bacteriana da Expressão Gênica , Nitrogênio/metabolismoRESUMO
When the wild type Cellulomonas flavigena was grown on glycerol, xylose or cellobiose, it produced basal levels of carboxymethyl-cellulase (CMCase), filter-paperase (FPase) and xylanase activities. By comparison, a catabolic derepressed mutant strain of the same organism produced markedly higher levels of these enzymes when grown on the same carbon sources. Sugar-cane bagasse induced both the wild type and the mutant strain to produce three- to eight-time higher levels of FPase and xylanase than was observed with xylose or cellobiose. Continuous culture was used to determine the minimal cellobiose or glucose concentrations that repress the enzyme synthesis in both strains. 2.5 g l(-1) glucose repressed FPase and xylanases from wild type, while 1.6 times more glucose was needed to repress the same activities in the PN-120 strain. In the same way, twofold more cellobiose was needed to reduce by 75% the CMCase and xylanase activities in the mutant compared to the wild type. The FPase in the presence of 4 g l(-1) cellobiose did not change in the same strain. Therefore, its derepressed and feedback resistant characters of PN-120 mutant are evident. On the other hand, isoelectrofocused crude extracts of mutant and wild strains induced by sugar-cane bagasse, did not show differences in protein patterns, however, the Schiffs staining was more intense in the PN-120 than in the wild strain. These results point out that the mutational treatment did not apparently change the extracellular proteins from mutant PN-120 and this could affect their regulation sites, since derepressed and feed-back resistant enzymes may be produced.
Assuntos
Actinomycetales/enzimologia , Actinomycetales/genética , Celulase/metabolismo , Celulose , Xilosidases/metabolismo , Actinomycetales/crescimento & desenvolvimento , Celulase/biossíntese , Repressão Enzimática , Glicosídeo Hidrolases/biossíntese , Glicosídeo Hidrolases/metabolismo , Cinética , Mutagênese , Papel , Especificidade por Substrato , Xilano Endo-1,3-beta-Xilosidase , Xilosidases/biossínteseRESUMO
The upstream activating region that controls cellulose-induced expression of the glucose-repressible cellobiohydrolase I gene (UARcb1) of the filamentous fungus Trichoderma reesei is shown to mediate transcription and glucose repression of a reporter gene in Saccharomyces cerevisiae, a unicellular microorganism that lacks the genes required for the utilization of cellulose. Glucose-controlled transcription mediated by UARcb1 requires the products of the genes SNF1 and SSN6, a protein kinase and a repressor, respectively, that regulate glucose-repressible yeast genes. Previously, it has been shown that mitochondrial function is implicated in cellobiohydrolase I gene expression in T. reesei and this sensitivity to the metabolic state of the mitochondria was shown to be transcriptionally controlled by the 5'-flanking sequence of the cbh1 gene [Abrahão-Neto et al. (1995) Biochemistry 34, 10456-10462]. Remarkably, transcription of the reporter gene controlled by UARcb1 in S. cerevisiae also showed a requirement for active mitochondria, suggesting that a common mechanism involving mitochondrial activity controls glucose-repressible genes in both microorganisms.
Assuntos
Celulase/genética , Proteínas de Ligação a DNA , Regulação Enzimológica da Expressão Gênica , Glucose/fisiologia , Mitocôndrias/genética , Proteínas Nucleares , Regiões Promotoras Genéticas , Proteínas Repressoras , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Trichoderma/genética , Regiões 5' não Traduzidas , Celulase/biossíntese , Celulose 1,4-beta-Celobiosidase , Eletroforese em Gel de Poliacrilamida , Ativação Enzimática/genética , Repressão Enzimática/genética , Proteínas Fúngicas/fisiologia , Heme/fisiologia , Óperon Lac , Mitocôndrias/enzimologia , Consumo de Oxigênio , Proteínas Serina-Treonina Quinases/fisiologia , Saccharomyces cerevisiae/enzimologia , Transcrição Gênica , Trichoderma/enzimologiaRESUMO
Random Tn917 mutagenesis of Bacillus subtilis followed by selection of lipoic acid auxotrophs led to the isolation of the cysH gene. The gene was sequenced and found to encode a phosphoadenylylsulfate sulfotransferase with a molecular mass of 27 kDa. Expression of lacZ fused to the cysH promoter was repressed by cysteine and sulfide and induced by sulfur limitation, indicating that cysH is controlled at the level of transcription.
Assuntos
Bacillus subtilis/genética , Cisteína/biossíntese , Genes Bacterianos , Sulfotransferases/genética , Sequência de Aminoácidos , Bacillus subtilis/efeitos dos fármacos , Bacillus subtilis/enzimologia , Sequência de Bases , Mapeamento Cromossômico , Clonagem Molecular , Cisteína/farmacologia , Repressão Enzimática , Escherichia coli/genética , Dados de Sequência Molecular , Mutação , Proteínas Recombinantes/biossíntese , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Sulfetos/farmacologia , Sulfotransferases/biossínteseRESUMO
A produçäo de amiloglicosidase por Aspergillus awamori NRRL3112 em processo descontínuo alimentado é 92 por cento superior em relaçäo ao processo descontínuo em cultivos com 20 g/l de concentraçäo total de fonte de carbono oriunda de farinha de mandioca. Uma análise da velocidade específica de produçäo mostra ser este resultado decorrente da reduçäo do efeito repressivo causado pela glicose, já que o efeito indutivo, relacionado à concentraçäo de polissacarídeo, também foi reduzido
Assuntos
Aspergillus/enzimologia , Proteínas de Transporte de Monossacarídeos/análise , Repressão EnzimáticaRESUMO
When grown on low-Pi medium, the chaA1 pabaA1 palB7 mutant of Aspergillus nidulans excretes an acid phosphatase with steady-state kinetic properties, temperature sensitivity and electrophoretic mobility different from those of the enzyme excreted by the pabaA1 strain. The enzyme excreted by the pabaA1 strain at pH 6.5 showed PNP-P activity with negative cooperativity (K0.5 = 0.87 +/- 0.06 mM, n = 0.68 +/- 0.03) whereas the enzyme excreted by the chaA1 pabaA1 palB7 mutant showed Michaelian kinetics (Km = 0.46 +/- 0.03 mM, n = 1.00 +/- 0.02). The apparent half-lives at 60 degrees C, pH 5.5, of acid phosphatase excreted by the pabaA1 and chaA1 pabaA1 palB7 strains were 58.6 +/- 4.9 min and 21.5 +/- 1.8 min, respectively. Furthermore, the electrophoretic mobility of acid phosphatases excreted by the palA1, palB7, palC4, palE11 and palF15 mutants of A. nidulans was altered and differed from the electrophoretic mobility of the enzyme excreted by the wild-type strain. Also, the palB7 mutation altered the electrophoretic pattern of acid phosphatases synthesized on high-Pi medium. These results are compatible with the post-translational modifications in the Pi-repressible phosphatases rather than with the action of gene palB in controlling the transcription of structural genes of these enzymes.