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At least 235 records · Page 13Linked to original sources
PubMed1992

Purification and characterization of a novel enoyl coenzyme A reductase from Streptomyces collinus.

A novel NADPH-dependent enoyl reductase, catalyzing the conversion of 1-cyclohexenylcarbonyl coenzyme A (1-cyclohexenylcarbonyl-CoA) to cyclohexylcarbonyl-CoA, was purified to homogeneity from Streptomyces collinus. This enzyme, a dimer with subunits of identical M(r) (36,000), exhibits a Km of 1.5 +/- 0.3 microM for NADPH and 25 +/- 3 microM for 1-cyclohexenylcarbonyl-CoA. It has a pH optimum of 7.5, is most active at 30 degrees C, and is inhibited by both divalent cations and thiol reagents. Two internal peptide sequences were obtained. Ansatrienin A (an antibiotic produced by S. collinus) contains a cyclohexanecarboxylic acid moiety, and it is suggested that the 1-cyclohexenylcarbonyl-CoA reductase described herein catalyzes the final reductive step in the conversion of shikimic acid into this moiety.

Amino Acid Sequence↗
PubMed1976

Biosynthesis of chloramphenicol in Streptomyces sp. 3022a. Identification of p-amino-L-phenylalanine as a product from the action of arylamine synthetase on chorismic acid.

Products obtained from the action of arylamine synthetase on [G-14C]chorismic acid were fractionated by gel filtration and ion exchange column chromatography to yield a partially purified radioactive component with an arylamine function. From its ultraviolet absorption spectrum and thin-layer chromatographic behaviour the product was considered to be p-aminophenylalanine and the identification was confirmed by co-crystallization with an authentic specimen. Specific deamination of the product with L-amino-acid oxidase indicated that it was the L-epimer. These results strengthen previous evidence that arylamine synthetase is at a branch point in the shikimic acid pathway, specifically diverting intermediates to the synthesis of chloramphenicol.

Amino Acid Oxidoreductases↗
PubMed2003

Constituents of Hypericum laricifolium and their cyclooxygenase (COX) enzyme activities.

Investigation of the aerial parts of the medicinal plant Hypericum laricifolium led to the isolation of two new natural products, hentriacontanyl caffeate (1a), nonacosanyl caffeate (1b). In addition, stigmasterol, beta-sitosterol, 3-epi-betulinic acid (2), caffeic acid (3), ferulic acid, docosanol, p-hydroxybenzoic acid, 3,4-dimethoxy benzoic acid, quercetin (4), quercetin-3-O-galactoside (5), quercetin-3-O-rutinoside (6), quercetin-3-O-rhamnoside (7), quercetin-3-O-glucuronide (8) and shikimic acid were also isolated. The structures were determined by 1D- and 2D-NMR, mass spectrometry, and chemical transformations. The anti-inflammatory effects of the isolated compounds were discussed briefly.

Animals↗
PubMed1999

Cloning of the transketolase gene and the effect of its dosage on aromatic amino acid production in Corynebacterium glutamicum.

Transketolase is a key enzyme of the non-oxidative pentose phosphate pathway. The effect of its overexpression on aromatic amino acid production was investigated in Corynebacterium glutamicum, a typical amino-acid-producing organism. For this purpose, the transketolase gene of the organism was cloned on the basis of its ability to complement a C. glutamicum transketolase mutant with pleiotropically shikimic-acid-requiring, ribose- and gluconic-acid-negative phenotype. The gene was shown by deletion mapping and complementation analysis to be located in a 3.2-kb XhoI-SalI fragment of the genome. Amplification of the gene by use of low-, middle-, and high-copy-number vectors in a C. glutamicum strain resulted in overexpression of transketolase activities as well as a protein of approximately 83kDa in proportion to the copy numbers. Introduction of the plasmids into a tryptophan and lysine co-producer resulted in copy-dependent increases in tryptophan production along with concomitant decreases in lysine production. Furthermore, the presence of the gene in high copy numbers enabled tyrosine, phenylalanine and tryptophan producers to accumulate 5%-20% more aromatic amino acids. These results indicate that overexpressed transketolase activity operates to redirect the glycolytic intermediates toward the nonoxidative pentose phosphate pathway in vivo, thereby increasing the intracellular level of erythrose 4-phosphate, a precursor of aromatic biosynthesis, in the aromatic-amino-acid-producing C. glutamicum strains.

Amino Acids↗
PubMed2006

Ring-closing metathesis-based synthesis of (3R,4R,5S)-4-acetylamino-5-amino-3-hydroxy- cyclohex-1-ene-carboxylic acid ethyl ester: a functionalized cycloalkene skeleton of GS4104.

(3R,4R,5S)-4-Acetylamino-5-amino-3-hydroxy-cyclohex-1-ene-carboxylic acid ethyl ester, a functionalized cyclohexene skeleton of GS4104, was diastereoselectively synthesized. A major advantage of this synthesis is the use of readily available L-serine to replace frequently used (-)-shikimic acid or (-)-quinic acid as the starting material. Ring-closing metathesis and diastereoselective Grignard reactions successfully served as the key steps. Absolute configurations of the key intermediates were confirmed by corresponding two-dimensional NMR studies.

Cyclization↗
PubMed1962

Tryptophan synthetase levels in Escherichia coli, Shigella dysenteriae, and transduction hybrids.

Eisenstein, Richard B. (Western Reserve University, Cleveland, Ohio) and Charles Yanofsky. Tryptophan synthetase levels in Escherichia coli, Shigella dysenteriae, and transduction hybrids. J. Bacteriol. 83:193-204. 1962-Shigella dysenteriae and Escherichia coli, strains K-12 and B, were found to produce low levels of tryptophan synthetase, although some hybrids, formed by the introduction of the gene cluster concerned with tryptophan synthesis from S. dysenteriae into E. coli, produced high levels of this enzyme system. A revertant obtained from a tryptophan-requiring mutant also formed high levels of tryptophan synthetase. The gene or genes responsible for high enzyme production in these strains was shown to be linked to the cluster of genes concerned with tryptophan synthesis. The cause of high enzyme production was investigated. Various lines of evidence, including stimulation of growth by tryptophan precursors, sensitivity to inhibition by 5-methyltryptophan, absence of accumulation of tryptophan, and repression of enzyme formation by anthranilic acid and tryptophan, suggested that high enzyme production in the strains examined results from a partial block in the tryptophan pathway and not from resistance to repression by tryptophan. The conversion of shikimic acid-5-phosphate to anthranilic acid appears to be the partially blocked reaction in the strains studied.

Enzymes↗
PubMedDate not supplied

Impact of glyphosate on the Bradyrhizobium japonicum symbiosis with glyphosate-resistant transgenic soybean: a minireview.

Glyphosate-resistant (GR) soybean [Glycine max (L.) Merr.] expressing an insensitive 5-enolpyruvylshikimic acid-3-phosphate synthase (EPSPS) gene has revolutionized weed control in soybean production. The soybean nitrogen fixing symbiont, Bradyrhizobium japonicum, possesses a glyphosate-sensitive enzyme and upon exposure to glyphosate accumulates shikimic acid and hydroxybenzoic acids such as protocatechuic acid (PCA), accompanied with B. japonicum growth inhibition and death at high concentrations. In a series of greenhouse and field experiments, glyphosate inhibited nodulation and nodule leghemoglobin content of GR soybean. Glyphosate accumulated in nodules of field-grown GR soybean, but its effect on nitrogenase activity of GR soybean was inconsistent in field studies. In greenhouse studies, nitrogenase activity of GR soybean following glyphosate application was transiently inhibited especially in early growth stages, with the greatest inhibition occurring under moisture stress. Studies using bacteroid preparations showed that the level of glyphosate inhibition of bacteroid nitrogenase activity was related to in vitro glyphosate sensitivity of the B. japonicum strains. These studies indicate the potential for reduced nitrogen fixation in the GR soybean system; however, yield reductions due to this reduced N2 fixation in early stages of growth have not been demonstrated.

Bradyrhizobium↗
PubMed1976

Oncogenic and tumor-promoting Spermatophytes and Pteridophytes and their active principles.

A survey and discussion are presented of plants classified as Spermatophyta and Pteridophyta, extracts of which have been shown to be oncogenic or tumor-promoting in animals. The active oncogenic and tumor-promoting principles, where known, have been identified. They represent tannins; pyrrolizidine, indole, tropolone, quinoline, purine, and benzophenanthridine alkaloids; nitroso compounds; triterpene glycosides; lignans; isoflavans; allyl benzenoids; simple (nu-pyrenes; and carbocyclic hydroxy acids. A total of 28 compounds of known structure have been identified as oncogens and several phorbol esters as tumor-promoters. Plants known to contain any of the 28 oncogens (excluding shikimic acid and caffeine) have been tabulated; they represent at least 454 species, 110 genera, and 34 families of Spermatophyta and Pteridophyta.

Animal Feed↗
PubMed1951

Inhibition of Escherichia coli by p-aminobenzoic acid and its reversal by p-hydroxybenzoic acid.

p-Aminobenzoic acid (PABA) exerts three metabolic effects on E. coli: it acts as a normal vitamin at low concentrations, as a source of another vitamin, p-hydroxybenzoic acid (POB), at moderate concentrations, and as a growth inhibitor at high concentrations (150 to 1600 microg./ml.). The inhibition is competitively reversed by POB in 1/100 the concentration of PABA. The inhibition is also reversed to a limited extent by shikimic acid and compound X, precursors of POB. p-Nitrobenzoic acid is an inhibitory competitor of both POB and PABA. The retardation of growth produced by PABA and other competitive analogues of POB (p-nitrobenzoic acid; 4,4'-dihydroxydiphenyl sulfone; phenosulfazole) is converted to complete bacteriostasis by the addition of L-aspartic acid in a remarkably low concentration (1 microg./ml.)) without change in the competitive ratio with POB. The mechanism underlying this synergism is not clear. In contrast to wild type, mutants that require POB not only are inhibited by much lower concentrations of the above analogues, but also show inhibition by weaker competitors of POB such as p-hydroxybenzenesulfonamide, p-chlorobenzoic acid, and p-fluorobenzoic acid.

4-Aminobenzoic Acid↗
PubMedDate not supplied

Effects of alpha-aminooxy-beta-phenylpropionic acid on phenylalanine metabolism in p-fluorophenylalanine sensitive and resistant tobacco cells.

A p-fluorophenylalanine (PFP) resistant cell line with high phenylalanine ammonia lyase (PAL) activity and wild type cells with low PAL activity were compared in their responses to PAL inhibition by alpha-aminooxy-beta-phenylpropionic acid (AOP). Inhibition of PAL reduced the levels of the main phenolic compounds to 30% of the controls. Free phenylalanine pools increased 17 fold in the resistant line and 6 fold in the sensitive line, respectively. The accumulation of phenylalanine did not reduce the flow of labeled shikimic acid into the aromatic amino acids tyrosine and phenylalanine. The results are discussed with respect to the feedback inhibition of chorismate mutase activity by phenylalanine and tyrosine in both cell lines.

Ammonia-Lyases↗
PubMed1990

Chorismic acid, a key metabolite in modification of tRNA.

Chorismic acid is the common precursor for the biosynthesis of the three aromatic amino acids as well as for four vitamins. Mutants of Escherichia coli defective in any of the genes involved in the synthesis of chorismic acid are also unable to synthesize uridine 5-oxyacetic acid (cmo5U) and its methyl ester (mcmo5U). Both modified nucleosides are normally present in the wobble position of some tRNA species. Mutants defective in any of the specific pathways leading to phenylalanine, tyrosine, tryptophan, folate, enterochelin, ubiquinone, and menaquinone have normal levels of cmo5U and mcmo5U in their tRNA. The presence of shikimic acid in the growth medium restores the ability of an aroD mutant to synthesize cmo5U, while O-succinylbenzoate, which is an early intermediate in the synthesis of menaquinone, does not. Thus, chorismic acid is a key metabolite in the synthesis of these two modified nucleosides in tRNA. The absence of chorismic acid blocks the formation of cmo5U and mcmo5U at the first step, which might be the formation of 5-hydroxyuridine. This results in an unmodified U in the wobble position of tRNA(1Val) and in most of the tRNAs normally containing cmo5U and mcmo5U. Since cmo5U and mcmo5U are synthesized under anaerobic conditions, the formation of these nucleosides does not require molecular oxygen. One of the carbon atoms of the side chain, --O--CH2--COOH, originates from the methyl group of methionine. The other carbon atom does not originate directly from the C-1 pool, from the carboxyl group methionine, or from bicarbonate. This metabolic link between intermediary metabolism and translation also exists for another member of the family Enterobacteriaceae, Salmonella typhimurium, as well as for the distantly related gram-positive organism Bacillus subtilis.

Bacillus subtilis↗
PubMed2004

Metabolic profiling of Medicago truncatula cell cultures reveals the effects of biotic and abiotic elicitors on metabolism.

GC-MS-based metabolite profiling was used to analyse the response of Medicago truncatula cell cultures to elicitation with methyl jasmonate (MeJa), yeast elicitor (YE), or ultraviolet light (UV). Marked changes in the levels of primary metabolites, including several amino acids, organic acids, and carbohydrates, were observed following elicitation with MeJa. A similar, but attenuated response was observed following YE elicitation, whereas little response was observed following UV elicitation. MeJa induced the accumulation of the triterpene beta-amyrin, a precursor to the triterpene saponins, and LC-MS analysis confirmed the accumulation of triterpene saponins in MeJa-elicited samples. In addition, YE induced a slight, but significant accumulation of shikimic acid, an early precursor to the phenylpropanoid pathway, which was also demonstrated to be YE-inducible by LC-MS analyses. Correlation analyses of metabolite relationships revealed perturbation of the glycine, serine, and threonine biosynthetic pathway, and suggested the induction of threonine aldolase activity, an enzyme as yet uncharacterized from plants. Members of the branched chain amino acid pathway accumulated in a concerted fashion, with the strongest correlation being that between leucine and isoleucine (r2=0.941). While UV exposure itself had little effect on primary metabolites, the experimental procedure, as revealed by control treatments, induced changes in several metabolites which were similar to those following MeJa elicitation. Sucrose levels were lower in MJ- and YE-elicited samples compared with control samples, suggesting that a portion of the effects observed on the primary metabolic pool are a consequence of fundamental metabolic repartitioning of carbon resources rather than elicitor-specific induction. In addition, beta-alanine levels were elevated in all elicited samples, which, when viewed in the context of other elicitation responses, suggests the altered metabolism of coenzyme A and its esters, which are essential in secondary metabolism.

Acetates↗
PubMed1998

A seven-gene locus for synthesis of phenazine-1-carboxylic acid by Pseudomonas fluorescens 2-79.

Pseudomonas fluorescens 2-79 produces the broad-spectrum antibiotic phenazine-1-carboxylic acid (PCA), which is active against a variety of fungal root pathogens. In this study, seven genes designated phzABCDEFG that are sufficient for synthesis of PCA were localized within a 6.8-kb BglII-XbaI fragment from the phenazine biosynthesis locus of strain 2-79. Polypeptides corresponding to all phz genes were identified by analysis of recombinant plasmids in a T7 promoter/polymerase expression system. Products of the phzC, phzD, and phzE genes have similarities to enzymes of shikimic acid and chorismic acid metabolism and, together with PhzF, are absolutely necessary for PCA production. PhzG is similar to pyridoxamine-5'-phosphate oxidases and probably is a source of cofactor for the PCA-synthesizing enzyme(s). Products of the phzA and phzB genes are highly homologous to each other and may be involved in stabilization of a putative PCA-synthesizing multienzyme complex. Two new genes, phzX and phzY, that are homologous to phzA and phzB, respectively, were cloned and sequenced from P. aureofaciens 30-84, which produces PCA, 2-hydroxyphenazine-1-carboxylic acid, and 2-hydroxyphenazine. Based on functional analysis of the phz genes from strains 2-79 and 30-84, we postulate that different species of fluorescent pseudomonads have similar genetic systems that confer the ability to synthesize PCA.

Amino Acid Sequence↗
PubMed1994

Cloning of a phenazine biosynthetic locus of Pseudomonas aureofaciens PGS12 and analysis of its expression in vitro with the ice nucleation reporter gene.

Pseudomonas aureofaciens PGS12 produces three phenazine antibiotics, in addition to siderophores, hydrogen cyanide, pyrrolnitrin, and indoleacetic acid. Tn5-259.7 transposon mutagenesis was carried out to identify and clone a chromosomal locus involved in phenazine biosynthesis. Three classes of mutants were obtained: mutants deficient in phenazine production (Phz-), mutants deficient in hydrogen cyanide production (HCN-), and mutants deficient in the production of both compounds. EcoRI DNA fragments that contained the transposon and flanking regions were cloned from three mutants with single-transposon insertions, one from each phenotypic class. Phenazine and hydrogen cyanide production was restored by complementation of Phz- or HCN- mutants with selected cosmids from a PGS12 genomic library. No cosmids that complemented the doubly deficient Phz-HCN- mutant were obtained. A promoterless ice nucleation reporter gene was inserted in a phenazine biosynthetic locus by Tn3-spice transposon mutagenesis of a cosmid which complemented a phenazine-minus mutant. Reporter gene fusions that expressed the ice nucleation phenotype and no longer complemented phenazine production were introduced into the PGS12 chromosome by marker exchange. The expression of this locus was then monitored under different culture conditions. Expression decreased at pH levels below 7, and it was not affected by iron. Shikimic acid and phenylalanine favored higher expression levels. Expression was reduced in media with low substrate concentrations, indicating the importance of nutrient availability.

Bacterial Outer Membrane Proteins↗
PubMed1998

Utilization of quinate and p-hydroxybenzoate by actinomycetes: key enzymes and taxonomic relevance.

474 strains of the actinomycete genera Streptomyces (including species of the former genera Chainia and Streptoverticillium), Pseudonocardia and Micromonospora were examined for their ability to degrade quinate (Q) and p-hydroxybenzoate (pHB); selected strains were also tested for their capacity to catabolize benzoate (B). Whereas in the case of Q (5-10 g/l of a mineral salts agar medium) the growth response signalizes assimilation, pHB has to be supplied in lower concentration (routinely 0.3 g/l together with small amounts of peptone and yeast extract in liquid broth), and its degradation has to be determined spectrophotometrically. 27% of the streptomycete strains were able to grow with Q, and 57% with pHB. The three strains of "Chainia" that were tested metabolized Q and pHB, but none of the fourty species of "Streptoverticillium" showed this ability. 80% of the 30 strains of Psn. autotrophica grew with Q, and 100% degraded pHB and B. Two of the five Micromonospora strains gave a positive response with pHB, but not with Q.-Toluene treated cells (preincubated with Q, pHB or B, respectively) gave a positive Rothera reaction with protocatechuate or catechol respectively, thus demonstrating that these organisms employed the beta-ketoadipate pathway (orthofission) for the degradation of Q, pHB and B. The assay of five relevant enzymes in cell-free extracts of nine selected organisms showed that in nocardioform actinomycetes (Pseudonocardia, Rhodococcus) all enzymes of the protocatechuate branch of the ketoadipate pathway seem to be induced by beta-ketoadipate as demonstrated here for protocatechuate-3,4-dioxygenase. In contrast, in Streptomyces this enzyme appears to be induced by its substrate, protocatechuate, whereas the regulation of the other enzymes of this pathway remains to be elucidated.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2007

Progress in type II dehydroquinase inhibitors: from concept to practice.

Scientists are concerned by an ever-increasing rise in bacterial resistance to antibiotics, particularly in diseases such as malaria, toxoplasmosis, tuberculosis, and pneumonia, where the currently used therapies become progressively less efficient. It is therefore necessary to develop new, safe, and more efficient antibiotics. Recently, the existence of the shikimic acid pathway has been demonstrated in certain parasites such as the malaria parasite. These types of parasites cause more than a million casualties per year, and their effects are particularly strong in people with a compromised immune system such as HIV patients. In such cases it is possible that inhibitors of this pathway could be active against a large variety of microorganisms responsible for the more opportunistic infections in HIV patients. Interest in this pathway has resulted in the development of a wide variety of inhibitors for the enzymes involved. This review covers recent progress made in the development of inhibitors of the third enzyme of this pathway, i.e., the type II dehydroquinase. The X-ray crystal structures of several dehydroquinases (Streptomyces coelicolor, Mycobacterium tuberculosis, etc.) with an inhibitor bound in the active site have recently been solved. These complexes identified a number of key interactions involved in inhibitor binding and have shed light on several aspects of the catalytic mechanism. These crystal structures have also proven to be a useful tool for the design of potent and selective enzyme inhibitors, a feature that will also be discussed.

Anti-Bacterial Agents↗