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Results for “Peptide Synthases”

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At least 19 recordsLinked to original sources
PubMed1977

Selective inhibition of gamma-glutamyl-cycle enzymes by substrate analogs.

Substrate analogs have been obtained that selectively inhibit the reactions of the gamma-glutamyl cycle or that are susceptible to only limited metabolism by the cycle. Thus, glutathione synthesis may be inhibited and analogs of glutathione may be synthesized that do not participate in transpeptidation. Specific inhibitors of gamma-glutamylcyclotransferase and 5-oxoprolinase have been obtained. The findings offer new approaches to the in vivo study of the cycle and also to the design of more specifically directed analogs of inhibitors such as methionine sulfoximine and 6-diazo-5-oxonorleucine.

Acyltransferases↗
PubMed1978

Trypsin peptide patterns of tryptophan synthase beta2 protein among four species of the Enterobacteriaceae.

The tryptophan synthase beta 2 protein (EC 4.2.1.20) of Escherichia coli, Enterobacter aerogenes, Serratia marcescens, and Erwinia carotovora was purified and compared. Two-dimensional total peptide patterns for each of the four beta2 proteins obtained after digestion with trypsin showed that approximately three quarters of the total peptides are common to all four peptides. Examination of only arginine-containing peptides showed that approximately half of these peptides are common. From a comparative standpoint, the data provide evidence that the primary structure of beta 2 proteins is relatively similar, indicating that the trpB cistron is evolutionarily conserved in the enteric bacteria group.

Bacterial Proteins↗
PubMed1979

Conservation of primary structure of the pyridoxyl peptide of Escherichia coli and Serratia marcescens tryptophan synthase beta2 protein.

Two labeled peptides were recovered from tryptic digests of the NaB3H4-reduced, performic acid-oxidized beta2 protein of Serratia marcescens tryptophan synthase. These two pyridoxyl peptides were identical except for the presence or absence of an NH2-terminal arginyl residue. Tryptic digestion of nonreduced, performic acid-oxidized protein allowed isolation of the peptides that comprise the two halves of the pyridoxyl peptide. The partial primary structure for this region of the protein was shown to be Arg-Glx-Asx-Ler-Leu-His(Gly,Gly,Ala,His)Lys(Pxy)-Thr-Asx-Glx-Val(Leu,Gly,Glx,Ala,Leu,Leu,Ala)Lys. All the data available indicate that the sequence is identical with the homologous region from the Escherichia coli enzyme.

Amino Acid Sequence↗
PubMed2026

A Wagner-Meerwein-Like Rearrangement Generates a Vinyl Group in the Biosynthesis of the Polychlorinated Lipopeptides Fischerazoles.

The discovery of structurally unusual natural products is a major inspiration in the search for novel enzymatic transformations. In this study, we employ stable isotope-labeled precursor feeding and metabolomics to reveal highly unusual cyanobacterial lipopeptides-fischerazoles A-C. These metabolites contain a polychlorinated fatty acyl-derived moiety with a vinyl branch and an N-methylated carboxamide-thiazole terminus. Most strikingly, stable-isotope-labeled precursor supplementation showed that during fischerazole biosynthesis, a linear, hexadecanoic acid-derived intermediate is processed to yield the ultimately branched alkyl moiety. The branched carbon becomes part of the vinyl group together with an S-adenosyl methionine (SAM)-derived carbon. A candidate polyketide synthase/non-ribosomal peptide synthetase (PKS/NRPS) fischerazoles biosynthetic gene cluster-fsh-was identified in the genome of the producing strain, Fischerella sp. PCC 9431. In vitro assays experimentally connected fsh genes to fischerazole biosynthesis and revealed that the SAM-dependent methyltransferase FshF catalyzes a Wagner-Meerwein-like rearrangement to generate the vinyl group from an ACP-tethered unsaturated fatty acid. The discovery of FshF, which is related to the well-characterized cyclopropane fatty acid synthases (CFASs), brings to light a new biocatalytic strategy for alkyl chain functionalization.

Lipopeptides↗
PubMed1979

Active site phosphohistidine peptides from red cell bisphosphoglycerate synthase and yeast phosphoglycerate mutase.

Bisphosphoglycerate synthase (glycerate-1,3-P2 yields glycerate-2,3-P2) and phosphoglycerate mutase (glycerate-3-P formed from glycerate-2-P) are both phosphorylated by substrates at a histidine residue forming covalent intermediates which have been shown to function in the phosphoryl transfer reactions catalyzed by these enzymes (Rose, Z. B., and Dube, S. (1976) J. Biol. Chem. 251, 4817--4822). We have phosphorylated bisphosphoglycerate synthase from horse red blood cells with [U-32P]glycerate-2,3-P2, digested with trypsin, and purified the phosphopeptide. The amino acid sequence of the phosphohistidine peptide has been determined to be: His-Gly-Gln-Gly-Ala-Trp-Asn-Lys. In like manner, a phosphohistidyl peptide has now been purified from yeast phosphoglycerate mutase, for which the amino acid sequence is known (Winn, S. I., Watson, H. C., Fothergill, L. A., and Harkins, R. N. (1977) Biochem. Soc. Trans. 5, 657-659). The amino acid composition of the phosphopeptide indicates that histidine-8 was phosphorylated. The sequence of this peptide is closely homologous with the active site peptide from bisphosphoglycerate synthase. In yeast phosphoglycerate mutase, the denatured phosphoenzyme hydrolyzes with a single rate constant of 2.02 X 10(-4) s-1 at pH 3, 45 degrees C. The relevance of these observations to the enzymatic mechanism is discussed.

Amino Acid Sequence↗
PubMed1979

Oxidative damage to neutrophils in glutathione synthetase deficiency.

Several episodes of neutropenia were observed in a child with glutathione synthetase deficiency (5-oxoprolinuria). Studies of the patient's glutathione-deficient neutrophils were undertaken to examine the responses of the cells to oxidative stress associated with phagocytosis. The patient's neutrophils contained 10--20% of normal glutathione content. Circulating neutrophils in infection-free periods appeared less mature than normal by morphologic criteria, suggesting increased cell turnover. The cells ingested particles, responded to chemotactic stimuli, and oxidized 1-14C glucose normally. However, following ingestion of particles, the cells accumulated excess hydrogen peroxide compared with normal cells, and showed impaired protein iodination and bacterial killing. Electron micrographs revealed damage to microtubules and membranous structures in the patient's neutrophils during phagocytosis. The level of glutathione in the cells appears inadequate to protect against peroxide generated during normal cell function, and the cells are thus damaged and rendered less effective in bacterial killing. The data provide evidence for a protective role of glutathione in normal neutrophil function.

Chemotaxis, Leukocyte↗
PubMed1978

Biochemical heterogeneity in glutathione synthetase deficiency.

Two different clinical syndromes are associated with glutathione synthetase deficiency, one presenting with hemolytic anemia and 5-oxoprolinuria, the other with isolated hemolysis. We have differentiated these disorders on an enzymatic basis. In 5-oxoprolinuria, all cell types examined have grossly deficient enzyme activity and glutathione content. In contrast, in the nonoxoprolinuric variant, erythrocytes have decreased enzyme activity and glutathione content, whereas nucleated cells maintain substantial levels of both. The enzyme in this disorder is unstable in vitro and has shortened survival in intact erythrocytes. Nucleated cells appear able to maintain sufficient enzyme activity and concentrations of glutathione to suppress overproduction of 5-oxoproline.

Erythrocytes↗
PubMed2026

Identification of a Nonribosomal Peptide Analog With Activity Against Multiple Gram-Positive Bacteria via a Synthetic Bioinformatic Natural Product Discovery Approach.

Nonribosomal peptide (NRP) antibiotics exhibit potent biological activities and are broadly used in clinical therapy. Because most microorganisms are difficult to culture and many antibiotic biosynthetic genes are silent, traditional activity tracking approaches face major limitations in the discovery of novel NRPs. Here, based on a synthetic bioinformatic natural product (syn-BNP) discovery approach that integrates bioinformatics and chemical synthesis, a novel nonribosomal peptide synthetase (NRPS) gene cluster from the genome of Rhodococcus erythropolis D-1 was mined. A putative NRP scaffold synthesized by the NRPS encoded by this cluster was predicted. Through chemical synthesis and four rounds of structure-activity relationship (SAR) studies, 37 NRP analogs were ultimately generated. Among these analogs, ZURJC28 shows activity against multiple Gram-positive bacteria, including two drug-resistant strains. Mechanistic studies and metabolomics analyses revealed that ZURJC28 exerts membrane-disruptive activity associated with interaction with phosphatidylglycerol (PG)-enriched Gram-positive membranes, leading to membrane damage and widespread metabolic dysregulation. ZURJC28 also shows low cytotoxicity and low hemolytic activity, suggesting its preliminary in vitro safety profile.

Gram-Positive Bacteria↗
PubMed1976

Derepression of certain aromatic amino acid biosynthetic enzymes of Escherichia coli K-12 by growth in Fe3+-deficient medium.

3-Deoxy-arabino-heptulosonic acid 7-phosphate synthase, prephenate dehydratase, tryptophan synthase, and 2,3-dihydroxybenzoylserine synthase enzyme activities are derepressed in wild-type Escherichia coli K-12 cells grown on Fe3+-deficient medium. This derepression is reversed when FeSO4 is added to the growth medium. Addition of shikimic acid to the Fe3+-deficient growth medium caused repression of the first three enzyme activities but not of 2,3-dihydroxybenzoylserine synthase activity. Addition of 2,3-dihydroxybenzoic acid to the Fe3+-deficient growth medium has no effect on any of the above-mentioned enzyme activities. The Fe3+ deficiency-mediated derepression of 3-deoxyarabino-heptulosonic acid 7-phosphate synthase activity is due to an elevation of the tyrosine-sensitive isoenzyme; the phenylalanine-sensitive isoenzyme is not derepressed under these conditions.

3-Deoxy-7-Phosphoheptulonate Synthase↗