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1.
Antimicrob Agents Chemother ; 68(8): e0172123, 2024 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-38990013

RESUMO

The use of ß-lactam/ß-lactamase inhibitors constitutes an important strategy to counteract ß-lactamases in multidrug-resistant (MDR) Gram-negative bacteria. Recent reports have described ceftazidime-/avibactam-resistant isolates producing CTX-M variants with different amino acid substitutions (e.g., P167S, L169Q, and S130G). Relebactam (REL) combined with imipenem has proved very effective against Enterobacterales producing ESBLs, serine-carbapenemases, and AmpCs. Herein, we evaluated the inhibitory efficacy of REL against CTX-M-96, a CTX-M-15-type variant. The CTX-M-96 structure was obtained in complex with REL at 1.03 Å resolution (PDB 8EHH). REL was covalently bound to the S70-Oγ atom upon cleavage of the C7-N6 bond. Compared with apo CTX-M-96, binding of REL forces a slight displacement of the deacylating water inwards the active site (0.81 Å), making the E166 and N170 side chains shift to create a proper hydrogen bonding network. Binding of REL also disturbs the hydrophobic patch formed by Y105, P107, and Y129, likely due to the piperidine ring of REL that creates clashes with these residues. Also, a remarkable change in the positioning of the N104 sidechain is also affected by the piperidine ring. Therefore, differences in the kinetic behavior of REL against class A ß-lactamases seem to rely, at least in part, on differences in the residues being involved in the association and stabilization of the inhibitor before hydrolysis. Our data provide the biochemical and structural basis for REL effectiveness against CTX-M-producing Gram-negative pathogens and essential details for further DBO design. Imipenem/REL remains an important choice for dealing with isolates co-producing CTX-M with other ß-lactamases.


Assuntos
Compostos Azabicíclicos , Inibidores de beta-Lactamases , beta-Lactamases , Compostos Azabicíclicos/farmacologia , Compostos Azabicíclicos/química , beta-Lactamases/genética , beta-Lactamases/metabolismo , beta-Lactamases/química , Inibidores de beta-Lactamases/farmacologia , Inibidores de beta-Lactamases/química , Cristalografia por Raios X , Antibacterianos/farmacologia , Imipenem/farmacologia , Imipenem/química , Ceftazidima/farmacologia , Testes de Sensibilidade Microbiana , Domínio Catalítico
2.
Biotechnol Bioeng ; 121(9): 2728-2741, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-38837223

RESUMO

Peroxyacid synthesis is the first step in Prilezhaev epoxidation, which is an industrial method to form epoxides. Motivated by the development of a kinetic model as a tool for solvent selection, the effect of solvent type and acid chain length on the lipase-catalyzed peroxyacid synthesis was studied. A thermodynamic activity-based ping-pong kinetic expression was successfully applied to predict the effect of the reagent loadings in hexane. The activity-based reaction quotients provided a prediction of solvent-independent equilibrium constants. However, this strategy did not achieve satisfactory estimations of initial rates in solvents of higher polarity. The lack of compliance with some assumptions of this methodology could be confirmed through molecular dynamics calculations i.e. independent solvation energies and lack of solvent interaction with the active site. A novel approach is proposed combining the activity-based kinetic expression and the free binding energy of the solvent with the active site to predict kinetics upon solvent change. Di-isopropyl ether generated a strong interaction with the enzyme's active site, which was detrimental to kinetics. On the other hand, toluene or limonene gave moderate interaction with the active site rendering improved catalytic yield compared with less polar solvents, a finding sharpened when peroctanoic acid was produced.


Assuntos
Lipase , Simulação de Dinâmica Molecular , Solventes , Solventes/química , Lipase/química , Lipase/metabolismo , Cinética , Compostos de Epóxi/química , Compostos de Epóxi/metabolismo , Proteínas Fúngicas/química , Proteínas Fúngicas/metabolismo
3.
Int J Biol Macromol ; 270(Pt 2): 132281, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38740150

RESUMO

DapE is a Zn2+-metallohydrolase recognized as a drug target for bacterial control. It is a homodimer that requires the exchange of interface strands by an induced fit essential for catalysis. Identifying novel anti-DapE agents requires greater structural details. Most of the characterized DapEs are from the Gram-negative group. Here, two high-resolution DapE crystal structures from Enterococcus faecium are presented for the first time with novel aspects. A loosened enzyme intermediate between the open and closed conformations is observed. Substrates may bind to loose state, subsequently it closes, where hydrolysis occurs, and finally, the change to the open state leads to the release of the products. Mutation of His352 suggests a role, along with His194, in the oxyanion stabilization in the mono-metalated Zn2+ isoform, while in the di-metalated isoform, the metal center 2 complements it function. An aromatic-π box potentially involved in the interaction of DapE with other proteins, and a peptide flip could determine the specificity in the Gram-positive ArgE/DapE group. Finally, details of two extra-catalytic cavities whose geometry changes depending on the conformational state of the enzyme are presented. These cavities could be a target for developing non-competitive agents that trap the enzyme in an inactive state.


Assuntos
Proteínas de Bactérias , Enterococcus faecium , Amidoidrolases/química , Amidoidrolases/metabolismo , Amidoidrolases/genética , Sequência de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Domínio Catalítico , Cristalografia por Raios X , Enterococcus faecium/enzimologia , Ligantes , Modelos Moleculares , Ligação Proteica , Conformação Proteica , Especificidade por Substrato , Zinco/química , Zinco/metabolismo
4.
Antimicrob Agents Chemother ; : e0172023, 2024 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-38690895

RESUMO

The PER-2 ß-lactamase is a unique class A enzyme conferring broad spectrum cephalosporin resistance. In this study, we explored the stability of cefiderocol (FDC) against PER-2 ß-lactamase to gain insights into structure activity relationships (SAR) of this synthetic siderophore-conjugated antibiotic. Herein, we show that the MICs of FDC for PER-2 producing isolates and transformants ranged between 0.125 and 64 µg/mL; diazabicyclooctanes (DBOs) reduced the MIC values. In PER-2 mutants, MIC values decreased up to 10-12 dilutions in agreement with previous observations especially in the case of Arg220 substitutions. Catalytic efficiency for PER-2 was 0.072 µM-1 s-1, comparable with PER-1 (0.046 µM-1 s-1) and NDM-1 (0.067 µM-1 s-1). In silico models revealed that FDC within the active site of PER-2 demonstrates unique interactions as a result of the inverted Ω loop fold and extension of the ß3-ß4 connecting loop.

5.
Int J Biol Macromol ; 259(Pt 1): 129226, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38184030

RESUMO

In higher eukaryotes and plants, the last two sequential steps in the de novo biosynthesis of uridine 5'-monophosphate (UMP) are catalyzed by a bifunctional natural chimeric protein called UMP synthase (UMPS). In higher plants, UMPS consists of two naturally fused enzymes: orotate phosphoribosyltransferase (OPRTase) at N-terminal and orotidine-5'-monophosphate decarboxylase (ODCase) at C-terminal. In this work, we obtained the full functional recombinant protein UMPS from Coffea arabica (CaUMPS) and studied its structure-function relationships. A biochemical and structural characterization of a plant UMPS with its two functional domains is described together with the presentation of the first crystal structure of a plant ODCase at 1.4 Å resolution. The kinetic parameters measured of CaOPRTase and CaODCase domains were comparable to those reported. The crystallographic structure revealed that CaODCase is a dimer that conserves the typical fold observed in other ODCases from prokaryote and eukaryote with a 1-deoxy-ribofuranose-5'-phosphate molecule bound in the active site of one subunit induced a closed conformation. Our results add to the knowledge of one of the key enzymes of the de novo biosynthesis of pyrimidines in plant metabolism and open the door to future applications.


Assuntos
Carboxiliases , Coffea , Orotato Fosforribosiltransferase/química , Orotato Fosforribosiltransferase/metabolismo , Orotidina-5'-Fosfato Descarboxilase/genética , Orotidina-5'-Fosfato Descarboxilase/química , Orotidina-5'-Fosfato Descarboxilase/metabolismo , Complexos Multienzimáticos/química , Proteínas Recombinantes/genética , Uridina Monofosfato
6.
FEBS Open Bio ; 13(5): 912-925, 2023 05.
Artigo em Inglês | MEDLINE | ID: mdl-36906930

RESUMO

Imidazole is largely employed in recombinant protein purification, including GH1 ß-glucosidases, but its effect on the enzyme activity is rarely taken into consideration. Computational docking suggested that imidazole interacts with residues forming the active site of the GH1 ß-glucosidase from Spodoptera frugiperda (Sfßgly). We confirmed this interaction by showing that imidazole reduces the activity of Sfßgly, which does not result from enzyme covalent modification or promotion of transglycosylation reactions. Instead, this inhibition occurs through a partial competitive mechanism. Imidazole binds to the Sfßgly active site, reducing the substrate affinity by about threefold, whereas the rate constant of product formation remains unchanged. The binding of imidazole within the active site was further confirmed by enzyme kinetic experiments in which imidazole and cellobiose competed to inhibit the hydrolysis of p-nitrophenyl ß-glucoside. Finally, imidazole interaction in the active site was also demonstrated by showing that it hinders access of carbodiimide to the Sfßgly catalytic residues, protecting them from chemical inactivation. In conclusion, imidazole binds in the Sfßgly active site, generating a partial competitive inhibition. Considering that GH1 ß-glucosidases share conserved active sites, this inhibition phenomenon is probably widespread among these enzymes, and this should be taken into account when considering the characterization of their recombinant forms.


Assuntos
Glucosídeos , beta-Glucosidase , beta-Glucosidase/química , beta-Glucosidase/metabolismo , Domínio Catalítico , Hidrólise , Imidazóis/farmacologia
7.
Biochem J ; 480(4): 259-281, 2023 02 27.
Artigo em Inglês | MEDLINE | ID: mdl-36727473

RESUMO

Neither the Pseudomonas aeruginosa aldehyde dehydrogenase encoded by the PA4189 gene nor its ortholog proteins have been biochemically or structurally characterized and their physiological function is unknown. We cloned the PA4189 gene, obtained the PA4189 recombinant protein, and studied its structure-function relationships. PA4189 is an NAD+-dependent aminoaldehyde dehydrogenase highly efficient with protonated aminoacetaldehyde and 3-aminopropionaldehyde, which are much more preferred to the non-protonated species as indicated by pH studies. Based on the higher activity with aminoacetaldehyde than with 3-aminopropionaldehyde, we propose that aminoacetaldehyde might be the PA4189 physiological substrate. Even though at the physiological pH of P. aeruginosa cells the non-protonated aminoacetaldehyde species will be predominant, and despite the competition of these species with the protonated ones, PA4189 would very efficiently oxidize ACTAL in vivo, producing glycine. To our knowledge, PA4189 is the first reported enzyme that might metabolize ACTAL, which is considered a dead-end metabolite because its consuming reactions are unknown. The PA4189 crystal structure reported here suggested that the charge and size of the active-site residue Glu457, which narrows the aldehyde-entrance tunnel, greatly define the specificity for small positively charged aldehydes, as confirmed by the kinetics of the E457G and E457Q variants. Glu457 and the residues that determine Glu457 conformation inside the active site are conserved in the PA4189 orthologs, which we only found in proteobacteria species. Also is conserved the PA4189 genomic neighborhood, which suggests that PA4189 participates in an uncharacterized metabolic pathway. Our results open the door to future efforts to characterize this pathway.


Assuntos
Aldeídos , Pseudomonas aeruginosa , Aldeídos/química , Propilaminas , Oxirredutases , Cinética , Especificidade por Substrato
8.
Foods ; 12(4)2023 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-36832976

RESUMO

The present work describes the purification of an enzyme capable of degrading punicalagin. The enzyme was produced by Aspergillus niger GH1 by solid-state fermentation, and the enzyme production was induced by using ellagitannins as the sole carbon source. The purification steps included the concentration by lyophilization, desalting, anionic exchange, and gel filtration chromatography. The enzyme kinetic constants were calculated by using punicalagin, methyl gallate, and sugar beet arabinans. The molecular mass of the protein was estimated by SDS-PAGE. The identified bands were excised and digested using trypsin, and the peptides were submitted to HPLC-MS/MS analysis. The docking analysis was conducted, and a 3D model was created. The purification fold increases 75 times compared with the cell-free extract. The obtained Km values were 0.053 mM, 0.53% and 6.66 mM for punicalagin, sugar beet arabinans and methyl gallate, respectively. The optimal pH and temperature for the reaction were 5 and 40 °C, respectively. The SDS-PAGE and native PAGE analysis revealed the presence of two bands identified as α-l-arabinofuranosidase. Both enzymes were capable of degrading punicalagin and releasing ellagic acid.

9.
Mar Drugs ; 21(2)2023 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-36827145

RESUMO

For decades, gorgonians and soft corals have been considered promising sources of bioactive compounds, attracting the interest of scientists from different fields. As the most abundant bioactive compounds within these organisms, terpenoids, steroids, and alkaloids have received the highest coverage in the scientific literature. However, enzyme inhibitors, a functional class of bioactive compounds with high potential for industry and biomedicine, have received much less notoriety. Thus, we revised scientific literature (1974-2022) on the field of marine natural products searching for enzyme inhibitors isolated from these taxonomic groups. In this review, we present representative enzyme inhibitors from an enzymological perspective, highlighting, when available, data on specific targets, structures, potencies, mechanisms of inhibition, and physiological roles for these molecules. As most of the characterization studies for the new inhibitors remain incomplete, we also included a methodological section presenting a general strategy to face this goal by accomplishing STRENDA (Standards for Reporting Enzymology Data) project guidelines.


Assuntos
Antozoários , Produtos Biológicos , Animais , Produtos Biológicos/farmacologia , Inibidores Enzimáticos , Esteroides , Antozoários/química , Terpenos
10.
Curr Med Chem ; 30(6): 669-688, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-35726411

RESUMO

BACKGROUND: Alzheimer's disease (AD) is a chronic neurodegenerative disease and the most common form of dementia, especially in the elderly. Due to the increase in life expectancy, in recent years, there has been an excessive growth in the number of people affected by this disease, causing serious problems for health systems. In recent years, research has been intensified to find new therapeutic approaches that prevent the progression of the disease. In this sense, recent studies indicate that the dual-specificity tyrosine phosphorylation regulated kinase 1A (DYRK1A) gene, which is located on chromosome 21q22.2 and overexpressed in Down syndrome (DS), may play a significant role in developmental brain disorders and early onset neurodegeneration, neuronal loss and dementia in DS and AD. Inhibiting DYRK1A may serve to stop the phenotypic effects of its overexpression and, therefore, is a potential treatment strategy for the prevention of ageassociated neurodegeneration, including Alzheimer-type pathology. OBJECTIVE: In this review, we investigate the contribution of DYRK1A inhibitors as potential anti-AD agents. METHODS: A search in the literature to compile an in vitro dataset including IC50 values involving DYRK1A was performed from 2014 to the present day. In addition, we carried out structure-activity relationship studies based on in vitro and in silico data. RESULTS: molecular modeling and enzyme kinetics studies indicate that DYRK1A may contribute to AD pathology through its proteolytic process, reducing its kinase specificity. CONCLUSION: further evaluation of DYRK1A inhibitors may contribute to new therapeutic approaches for AD.


Assuntos
Doença de Alzheimer , Inibidores de Proteínas Quinases , Idoso , Humanos , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/patologia , Encéfalo/patologia , Fosforilação , Inibidores de Proteínas Quinases/farmacologia , Quinases Dyrk
11.
Bioorg Chem ; 129: 106204, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36306699

RESUMO

The renin-angiotensin system (RAS) is a key regulator of human arterial pressure. Several of its effects are modulated by angiotensin II, an octapeptide originating from the action of angiotensin-I converting enzyme (ACE) on the decapeptide angiotensin-I. ACE possess two active sites (nACE and cACE) that have their own kinetic and substrate specificities. ACE inhibitors are widely used as the first-line treatment for hypertension and other heart-related diseases, but because they inactivate both ACE domains, their use is associated with serious side effects. Thus, the search for domain-specific ACE inhibitors has been the focus of intense research. Angiotensin (1-7), a peptide that also belongs to the RAS, acts as a substrate of nACE and an inhibitor of cACE. We have synthetized 15 derivatives of Ang (1-7), sequentially removing the N-terminal amino acids and modifying peptides extremities, to find molecules with improved selectivity and inhibition properties. Ac-Ang (2-7)-NH2 is a good ACE inhibitor, resistant to cleavage and with improved cACE selectivity. Molecular dynamics simulations provided a model for this peptide's selectivity, due to Val3 and Tyr4 interactions with ACE subsites. Val3 has an important interaction with the S3 subsite, since its removal greatly reduced peptide-enzyme interactions. Taken together, our findings support ongoing studies using insights from the binding of Ac-Ang (2-7)-NH2 to develop effective cACE inhibitors.


Assuntos
Angiotensina I , Peptidil Dipeptidase A , Humanos , Peptidil Dipeptidase A/metabolismo , Angiotensina I/farmacologia , Inibidores da Enzima Conversora de Angiotensina/química , Peptídeos/farmacologia
12.
Clin Biochem ; 109-110: 64-73, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36089067

RESUMO

BACKGROUND: Newborn screening for glucose-6-phosphate dehydrogenase deficiency (G6PDd) was implemented in Mexico beginning in 2017. In a Mexican population, genotyping analysis of G6PD as a second-tier method identified a previously unreported missense variant, p.(Ser184Cys), which we propose to call "Toluca", and the extremely rare p.(Gln195His) or "Tainan" variant, which was previously described in the Taiwanese population as a Class II allele through in silico evaluations. Here, we sought to perform in vitro biochemical characterizations of the Toluca and Tainan G6PD natural variants and describe their associated phenotypes. METHODS: The "Toluca" and "Tainan" variants were identified in three unrelated G6PDd newborn males, two of whom lacked evidence of acute hemolytic anemia (AHA) or neonatal hyperbilirubinemia (NHB). We constructed wild-type (WT), Tainan, and Toluca G6PD recombinant enzymes and performed in vitro assessments. RESULTS: Both variants had diminished G6PD expression, decreased affinities for glucose-6-phosphate and NADP+ substrates, significant decreases in catalytic efficiency (∼97 % with respect to WT-G6PD), and diminished thermostabilities that were partially rescued by NADP+. In silico protein modeling predicted that the variants would have destabilizing effects on the protein tertiary structure, potentially reducing the enzyme half-lives and/or catalytic efficiencies. CONCLUSION: Our data suggest that G6PD "Tainan" and "Toluca" are potential Class II natural variants, which agrees with the absence of chronic nonspherocytic hemolytic anemia (CNSHA) in our patients. It remains to be determined whether these variants represent high-risk genetic factors for developing CNSHA, AHA, and/or NHB.


Assuntos
Deficiência de Glucosefosfato Desidrogenase , Humanos , Masculino , Recém-Nascido , Deficiência de Glucosefosfato Desidrogenase/diagnóstico , Deficiência de Glucosefosfato Desidrogenase/genética , Glucosefosfato Desidrogenase/genética , Glucosefosfato Desidrogenase/química , Triagem Neonatal , NADP , México
13.
Pestic Biochem Physiol ; 187: 105188, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36127063

RESUMO

Pest management is challenged with resistant herbivores and problems regarding human health and environmental issues. Indeed, the greatest challenge to modern agriculture is to protect crops from pests and still maintain environmental quality. This study aimed to analyze by in silico, in vitro, and in vivo approaches to the feasibility of using the inhibitory protein extracted from mammals - Bovine Pancreatic Trypsin Inhibitor (BPTI) as a potential inhibitor of digestive trypsins from the pest Anticarsia gemmatalis and comparing the results with the host-plant inhibitor - Soybean Kunitz Trypsin Inhibitor (SKTI). BPTI and SKTI interacts with A. gemmatalis trypsin-like enzyme competitively, through hydrogen and hydrophobic bonds. A. gemmatalis larvae exposed to BPTI did not show two common adaptative mechanisms i.e., proteolytic degradation and overproduction of proteases, presenting highly reduced trypsin-like activity. On the other hand, SKTI-fed larvae did not show reduced trypsin-like activity, presenting overproduction of proteases and SKTI digestion. In addition, the larval survival was reduced by BPTI similarly to SKTI, and additionally caused a decrease in pupal weight. The non-plant protease inhibitor BPTI presents intriguing element to compose biopesticide formulations to help decrease the use of conventional refractory pesticides into integrated pest management programs.


Assuntos
Agentes de Controle Biológico , Glycine max , Mariposas , Praguicidas , Animais , Aprotinina/farmacologia , Agentes de Controle Biológico/farmacologia , Bovinos , Hidrogênio/farmacologia , Larva , Peptídeo Hidrolases/metabolismo , Praguicidas/farmacologia , Inibidores de Proteases/farmacologia , Tripsina , Inibidores da Tripsina/farmacologia
14.
Int J Mol Sci ; 23(13)2022 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-35806299

RESUMO

Thimet oligopeptidase (TOP) is a metallopeptidase involved in the metabolism of oligopeptides inside and outside cells of various tissues. It has been proposed that substrate or inhibitor binding in the TOP active site induces a large hinge-bending movement leading to a closed structure, in which the bound ligand is enclosed. The main goal of the present work was to study this conformational change, and fluorescence techniques were used. Four active TOP mutants were created, each equipped with a single-Trp residue (fluorescence donor) and a p-nitro-phenylalanine (pNF) residue as fluorescence acceptor at opposite sides of the active site. pNF was biosynthetically incorporated with high efficiency using the amber codon suppression technology. Inhibitor binding induced shorter Donor-Acceptor (D-A) distances in all mutants, supporting the view that a hinge-like movement is operative in TOP. The activity of TOP is known to be dependent on the ionic strength of the assay buffer and D-A distances were measured at different ionic strengths. Interestingly, a correlation between the D-A distance and the catalytic activity of TOP was observed: the highest activities corresponded to the shortest D-A distances. In this study for the first time the hinge-bending motion of a metallopeptidase in solution could be studied, yielding insight about the position of the equilibrium between the open and closed conformation. This information will contribute to a more detailed understanding of the mode of action of these enzymes, including therapeutic targets like neurolysin and angiotensin-converting enzyme 2 (ACE2).


Assuntos
Metaloendopeptidases , Oligopeptídeos , Domínio Catalítico , Ligantes , Metaloendopeptidases/química , Oligopeptídeos/metabolismo , Especificidade por Substrato
15.
Plant Cell Physiol ; 63(8): 1140-1155, 2022 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-35765894

RESUMO

In plants, it is well-known that ascorbic acid (vitamin C) can be synthesized via multiple metabolic pathways but there is still much to be learned concerning their integration and control mechanisms. Furthermore, the structural biology of the component enzymes has been poorly exploited. Here we describe the first crystal structure for an L-galactose dehydrogenase [Spinacia oleracea GDH (SoGDH) from spinach], from the D-mannose/L-galactose (Smirnoff-Wheeler) pathway which converts L-galactose into L-galactono-1,4-lactone. The kinetic parameters for the enzyme are similar to those from its homolog from camu camu, a super-accumulator of vitamin C found in the Peruvian Amazon. Both enzymes are monomers in solution and have a pH optimum of 7, and their activity is largely unaffected by high concentrations of ascorbic acid, suggesting the absence of a feedback mechanism acting via GDH. Previous reports may have been influenced by changes of the pH of the reaction medium as a function of ascorbic acid concentration. The structure of SoGDH is dominated by a (ß/α)8 barrel closely related to aldehyde-keto reductases (AKRs). The structure bound to NAD+ shows that the lack of Arg279 justifies its preference for NAD+ over NADP+, as employed by many AKRs. This favors the oxidation reaction that ultimately leads to ascorbic acid accumulation. When compared with other AKRs, residue substitutions at the C-terminal end of the barrel (Tyr185, Tyr61, Ser59 and Asp128) can be identified to be likely determinants of substrate specificity. The present work contributes toward a more comprehensive understanding of structure-function relationships in the enzymes involved in vitamin C synthesis.


Assuntos
Galactose Desidrogenases , Galactose , Ácido Ascórbico/metabolismo , Galactose/metabolismo , Galactose Desidrogenases/metabolismo , Manose/metabolismo , NAD
16.
FEMS Yeast Res ; 22(1)2022 04 08.
Artigo em Inglês | MEDLINE | ID: mdl-35266531

RESUMO

The first committed step in the leucine biosynthetic pathway is catalyzed by α-isopropylmalate synthase (α-IPMS, EC 2.3.3.13), which in the Saccaromycotina subphylum of Ascomycete yeasts is frequently encoded by duplicated genes. Following a gene duplication event, the two copies may be preserved presumably because the encoded proteins diverge in either functional properties and/or cellular localization. The genome of the petite-negative budding yeast Lachancea kluyveri includes two SAKL0E10472 (LkLEU4) and SAKL0F05170 g (LkLEU4BIS) paralogous genes, which are homologous to other yeast α-IPMS sequences. Here, we investigate whether these paralogous genes encode functional α-IPMS isozymes and whether their functions have diverged. Molecular phylogeny suggested that the LkLeu4 isozyme is located in the mitochondria and LkLeu4BIS in the cytosol. Comparison of growth rates, leucine intracellular pools and mRNA levels, indicate that the LkLeu4 isozyme is the predominant α-IPMS enzyme during growth on glucose as carbon source. Determination of the kinetic parameters indicates that the isozymes have similar affinities for the substrates and for the feedback inhibitor leucine. Thus, the diversification of the physiological roles of the genes LkLEU4 and LkLEU4BIS involves preferential transcription of the LkLEU4 gene during growth on glucose and different subcellular localization, although ligand interactions have not diverged.


Assuntos
2-Isopropilmalato Sintase , Saccharomycetales , 2-Isopropilmalato Sintase/química , 2-Isopropilmalato Sintase/genética , 2-Isopropilmalato Sintase/metabolismo , Glucose/metabolismo , Isoenzimas/genética , Isoenzimas/metabolismo , Leucina/metabolismo , Saccharomyces cerevisiae/metabolismo , Saccharomycetales/metabolismo
17.
Int J Mol Sci ; 23(3)2022 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-35163274

RESUMO

Eukarya pyruvate kinases possess glutamate at position 117 (numbering of rabbit muscle enzyme), whereas bacteria have either glutamate or lysine. Those with E117 are K+-dependent, whereas those with K117 are K+-independent. In a phylogenetic tree, 80% of the sequences with E117 are occupied by T113/K114/T120 and 77% of those with K117 possess L113/Q114/(L,I,V)120. This work aims to understand these residues' contribution to the K+-independent pyruvate kinases using the K+-dependent rabbit muscle enzyme. Residues 117 and 120 are crucial in the differences between the K+-dependent and -independent mutants. K+-independent activity increased with L113 and Q114 to K117, but L120 induced structural differences that inactivated the enzyme. T120 appears to be key in folding the protein and closure of the lid of the active site to acquire its active conformation in the K+-dependent enzymes. E117K mutant was K+-independent and the enzyme acquired the active conformation by a different mechanism. In the K+-independent apoenzyme of Mycobacterium tuberculosis, K72 (K117) flips out of the active site; in the holoenzyme, K72 faces toward the active site bridging the substrates through water molecules. The results provide evidence that two different mechanisms have evolved for the catalysis of this reaction.


Assuntos
Piruvato Quinase/genética , Piruvato Quinase/metabolismo , Piruvato Quinase/ultraestrutura , Sequência de Aminoácidos/genética , Animais , Apoenzimas/metabolismo , Sítios de Ligação , Catálise , Domínio Catalítico , Ácido Glutâmico/metabolismo , Lisina/metabolismo , Modelos Moleculares , Mycobacterium tuberculosis/enzimologia , Mycobacterium tuberculosis/genética , Filogenia , Potássio/metabolismo , Conformação Proteica , Coelhos
18.
Xenobiotica ; 52(12): 1011-1019, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36594659

RESUMO

Uridine diphosphate glucuronosyltransferase (UGT) enzymes conjugate many lipophilic chemicals, such as drugs, environmental contaminants, and endogenous compounds, promoting their excretion. The complexity of UGT kinetics, and the location of enzyme active site in endoplasmic reticulum lumen, requires an accurate optimisation of enzyme assays.In the present study, we characterised UGT activity in liver microsomes of green turtles (Chelonia mydas), an endangered species. The conditions for measuring UGT activity were standardised through spectrofluorimetric methods, using the substrates 4-methylumbelliferone (4-MU) and uridine diphosphate glucuronic acid (UDPGA) at 30 °C and pH 7.4.The green turtles showed UGT activity at the saturating concentrations of substrates of 250 µM to 4-MU and 7 mM to UDPGA. The alamethicin, Brij®58, bovine serum albumin (BSA), and magnesium increased UGT activity. The assay using alamethicin (22 µg per mg of protein), magnesium (1 mM), and BSA (0.25%) reached the highest Vmax (1203 pmol·min-1mg·protein-1). Lithocholic acid and diclofenac inhibited UGT activity in green turtles.This study is the first report of UGT activity in the liver of green turtles and provides a base for future studies to understand the mechanisms of toxicity by exposure to contaminants in this charismatic species.


Assuntos
Tartarugas , Uridina Difosfato Ácido Glucurônico , Animais , Uridina Difosfato Ácido Glucurônico/metabolismo , Tartarugas/metabolismo , Magnésio , Difosfato de Uridina , Glucuronosiltransferase/metabolismo , Microssomos Hepáticos/metabolismo , Alameticina/farmacologia
19.
Biochim Biophys Acta Biomembr ; 1864(2): 183822, 2022 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-34826402

RESUMO

Cu+-ATPases are integral membrane proteins belonging to the IB subfamily of the P-type ATPases that couple Cu+ transport to the hydrolysis of ATP. As some structural and functional particularities arise for Cu+-ATPases, several authors suggest that some of the reaction steps of the Albers-Post model postulated for other P-ATPases may be different. In this work we describe a functional characterization of Legionella pneumophila Cu+-ATPase (LpCopA), the first PIB-ATPase whose structure was determined by X-ray crystallography. Cu+-ATPase activity of the enzyme presents a maximum at ∼37 °C and pH 6.6-6.8. Phospholipids enhance LpCopA Cu+-ATPase activity in a non-essential mode where optimal activity is achieved at an asolectin molar fraction of 0.15 and an amphiphile-protein ratio of ~30,000. As described for other P-ATPases, Mg2+ acts as an essential activator. Furthermore, Cu+-ATPase activity dependence on [Cu+] and [ATP] can both be described by a sum of two hyperbolic functions. Based on that, and the [Cu+] and [ATP] dependencies of the best fitting parameters of the hyperbolae pointed above, we propose a minimal reaction scheme for the catalytic mechanism that shares the basic reaction steps of the Albers-Post model for P-type ATPases. The reaction scheme postulated contemplates two different binding affinities for a single ATP (apparent affinities of 0.66 and 550 µM at [Cu+] â†’ ∞) and binding of at least 2 Cu+ with different affinities as well (apparent affinities of 1.4 and 102.5 µM at [ATP] â†’ ∞).


Assuntos
Adenosina Trifosfatases/metabolismo , Trifosfato de Adenosina/metabolismo , Proteínas de Transporte de Cátions/metabolismo , Cobre/metabolismo , Legionella pneumophila/enzimologia , Transporte de Íons , Cinética , Modelos Moleculares , Ligação Proteica
20.
J Cell Biochem ; 123(4): 701-718, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-34931340

RESUMO

Acetylation of proteins seems a widespread process found in the three domains of life. Several studies have shown that besides histones, acetylation of lysine residues also occurs in non-nuclear proteins. Hence, it has been suggested that this covalent modification is a mechanism that might regulate diverse metabolic pathways by modulating enzyme activity, stability, and/or subcellular localization or interaction with other proteins. However, protein acetylation levels seem to have low correlation with modification of enzyme activity and pathway fluxes. In addition, the results obtained with mutant enzymes that presumably mimic acetylation have frequently been over-interpreted. Moreover, there is a generalized lack of rigorous enzyme kinetic analysis in parallel to acetylation level determinations. The purpose of this review is to analyze the current findings on the impact of acetylation on metabolic enzymes and its repercussion on metabolic pathways function/regulation.


Assuntos
Redes e Vias Metabólicas , Processamento de Proteína Pós-Traducional , Acetilação , Histonas , Cinética
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