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J C Vederas

Publications and source records attributed to J C Vederas.

47 records · Page 3Linked to original sources
PubMed1986

Analogs of diaminopimelic acid as inhibitors of meso-diaminopimelate decarboxylase from Bacillus sphaericus and wheat germ.

Analogs (1----6) of diaminopimelic acid have been synthesized and tested for inhibition of meso-diaminopimelate decarboxylases from Bacillus sphaericus IFO 3525 and from wheat germ (Triticum vulgaris). Difluoromethyl diaminopimelate 1 does not irreversibly inactivate or strongly competitively inhibit either enzyme. Lanthionine sulfoxides (2ab, 2c, and 2d) are good competitive inhibitors (about 50% inhibition at 1 mM) of both decarboxylases. The meso and LL-isomers of lanthionine sulfone (3ab and 3c) and lanthionine (6ab and 6c) are weaker competitive inhibitors (about 50% inhibition at 10-20 mM). The corresponding DD-isomers (3d and 6d) are less effective. The N-modified analogs are the most potent competitive inhibitors. The inhibition constant (Ki) values for B. sphaericus and wheat germ decarboxylases with N-hydroxydiaminopimelate 4 (mixture of isomers) are 0.91 and 0.71 mM, respectively; for the N-aminodiaminopimelate 5 (mixture of isomers) the Ki values are 0.10 and 0.084 mM, respectively. These N-modified analogs do not effectively inhibit L-lysine decarboxylase. None of the compounds showed any time-dependent inactivation of the decarboxylases, in contrast to behavior of other pyridoxal phosphate-dependent enzymes with analogous substrate derivatives. Possible mechanisms of inhibition are discussed. In preliminary tests for antibiotic activity 4 and 5 both gave 75% growth inhibition of Bacillus megaterium at 20 micrograms/ml in defined media. Other analogs (1----3) showed essentially no antibacterial activity.

Amino Acids, Diamino↗
PubMed1986

Inhibition of L-lysine uptake by alpha-methyl lysine in Escherichia coli and Bacillus sphaericus.

alpha-Methyl lysine was investigated as a potential inhibitor of lysine transport in Escherichia coli and Bacillus sphaericus. At equimolar concentrations, no inhibition was observed in either organism, but at 10X and 100X the lysine concentration, alpha-methyl lysine caused a 20-50% reduction in the initial rate of lysine uptake in both bacteria. A similar inhibitory effect was observed with epsilon-N-methyl lysine on lysine uptake in B. sphaericus, but not in E. coli. alpha-Methyl lysine had a reduced effect on ornithine uptake and no effect on arginine transport in either bacterium.

Arginine↗
PubMed1985

An acid metabolite of cyclosporine.

The primary biliary metabolite of cyclosporine has been isolated from rabbit and human bile. The material has been identified by mass spectrometry and by nuclear magnetic resonance spectrometry as an acidic metabolite of cyclosporine in which the eta-methyl group of the cyclosporine-specific nine carbon amino acid #1 has been oxidized to an alpha, beta unsaturated carboxylic acid functionality. This major cyclosporine metabolite is inactive in a phytohemagglutinin stimulated lymphocyte proliferation assay.

Animals↗
PubMed1985

Stereochemistry of lysine formation by meso-diaminopimelate decarboxylase from wheat germ: use of 1H-13C NMR shift correlation to detect stereospecific deuterium labeling.

The stereochemical course of the wheat germ meso-diaminopimelate (DAP) decarboxylase reaction is compared to that of the decarboxylase isolated from Bacillus sphaericus, which has been reported to proceed with an unusual inversion of configuration [Asada, Y., Tanizawa, K., Sawada, S., Suzuki, T., Misono, H., & Soda, K. (1981) Biochemistry 20, 6881-6886]. Reaction of each enzyme with either unlabeled diaminopimelic acid in D2O or [2,6-2H2]diaminopimelic acid in H2O gave stereospecifically deuterium-labeled lysine samples that were derivatized with (-)-camphanoyl chloride and diazomethane. Analysis by two-dimensional 1H-13C heteronuclear NMR shift correlation spectroscopy with 2H decoupling confirmed the stereochemistry of the B. sphaericus enzyme reaction and showed that the eukaryotic wheat germ meso-DAP decarboxylase also operates with inversion of configuration. This suggests similar mechanisms for the prokaryotic and eukaryotic enzymes and contrasts the retention mode observed with other pyridoxal phosphate dependent alpha-decarboxylases.

Bacterial Proteins↗
PubMed1979

Stereospecificity of sodium borohydride reduction of tyrosine decarboxylase from Streptococcus faecalis.

Sodium boro[3H]hydride reduction of tyrosine decarboxylase from Streptococcus faecalis followed by complete hydrolysis of the enzyme produces epsilon-[3H]pyridoxyllysine. Degradation of this material to [4'-3H]pyridoxamine and stereochemical analysis with apoaspartate aminotransferase shows that the re side at C-4' of the cofactor is exposed to solvent at pH 5.5 and 7.0. After binding of L-tyrosine at pH 5.5 or tyramine at pH 7.0 to the holoenzyme, sodium boro[3H]hydride reduction proceeds from the si face at C-4' of the substrate . cofactor complex. This indicates one of two conformational changes occurs upon binding of substrate; either rotation about the C-4 to C-4' bond in the cofactor or rotation about the axis through the C-5 and C-5' bond.

Binding Sites↗
PubMed1978

Stereochemistry and mechanism of reactions catalyzed by tryptophanase Escherichia coli.

Several beta replacement and alpha,beta elimination reactions catalyzed by tryptophanase from Escherichia coli are shown to proceed stereospecifically with retention of configuration. These conversions include synthesis of tryptophan from (2S,3R)- and (2s,3s)-[3(-3H)]serine in the presence of indole, deamination of these serines in D2O to pyruvate and ammonia, and cleavage of (2S,3R)-and (2S,3S)-[3(-3H)]tryptophan in D2O to indole, pyruvate, and ammonia. A coupled reaction with lactate dehydrogenase was used to trap the stereospecifically labeled [3-H,2H,3H]pryuvates as lactate, which was oxidized to acetate for chirality analysis of the methyl group. During deamination of tryptophan there is significant intramolecular transfer of the alpha proton of the amino acid to C-3 of indole. To determine the exposed face of the cofactor.substrate complex on the enzyme surface and to analyze its conformational orientation, sodium boro[3H]hydride was used to reduce tryptophanase-bound alaninepyridoxal phosphate Schiff's base. Degradation of the resulting pyridoxylalanine to (2S)-[2(-3H)]alanine and (4'S)-[4'(-3H)]pyridoxamine demonstrates that reduction occurs from the exposed si face at C-4' of the complex and that the ketimine double bond is trans.

Carbon Radioisotopes↗
PubMedDate not supplied

Further studies on the biosynthesis of granaticin.

Experiments with cerulenin-inhibited cultures of S. violaceoruber showed conversion of dihydrogranaticin (II) into granaticin (I), but not vice versa, confirming an earlier conclusion that II is the biosynthetic precursor of I. Feeding of CH3(13)C18O2Na followed by 13C-NMR analysis of the product by the 18O shift method indicated the expected incorporation of 18O at carbons 1, 11 and 13 of I and showed that the oxygen of the pyran ring originates from C-3 and not from C-15. Analysis of I biosynthesized from 13C2H3COONa by 13C[1H, 2H] triple resonance NMR spectroscopy showed the incorporation of one atom of deuterium each at C-2 and C-4. C-16 carried a maximum of 2, not 3, atoms of deuterium. These results are discussed in terms of biosynthetic mechanisms.

Acetates↗