The l-amino acid ligase RizA from B. subtilis selectively synthesizes dipeptides containing an N-terminal arginine. Many arginyl have salt-taste enhancing properties while Arg-Phe has been found to antihypertensive effect. A total of 21 variants were created by site-directed mutagenesis eight amino acids in the substrate binding pocket. recombinantly produced E. coli and purified affinity chrom...

The emergence of biochemical homochirality was a key step in the origin of life, yet prebiotic mechanisms for chiral separation are not well constrained. Here we demonstrate a geochemically plausible scenario for chiral separation of amino acids by adsorption on mineral surfaces. Crystals of the common rock-forming mineral calcite (CaCO(3)), when immersed in a racemic aspartic acid solution, di...

Within the past year the mode of action of biotin has become increasingly clarified. The relation of this vitamin to oxalacetic acid decarboxylation was discovered independently in at least four laboratories (l-l), while its apparent role in the synthesis of oleic acid has been suggested by Williams et al. (5) and Snell et al. (6). Biotin has further been shown to activate the deamination of as...

In continuation of previous studies, the intraarterial fusion of L-glutamic acid for 24 hr was found to oppose the decrease in acetylcholinesterase and butyrylcholinesterase in the superior cervical ganglion of the cat that otherwise occurs 48 hr after preganglionic denervation. The combination of glutamic acid and gamma-aminobutyric acid, in concentrations that were inactive individually, like...

A mutant of Escherichia coli that lacks leucyl-, phenylalanyl-transfer ribonucleic acid-protein transferase had diminished activities of L-phenylalanyl-transfer ribonucleic acid synthetase and tryptophanase, grew faster than its parent with aspartic acid as the sole nitrogen source, accumulated higher levels of enterochelin in the medium during iron limitation, and exhibited an abnormal morphol...

Synthesis of optically pure a-tert-butyl 0-methyl (2S,3R)-3-ethylhexahydroquinolinate (18) in 54-59% yield from L-aspartic acid was the foundation for a practical synthesis of (+)-vincamine. Conversion of L-aspartic acid to 18 was accomplished via two routes. In the first route, esterification was followed by mono-N-alkylation to attach the three-carbon residue. Nitrogen protection and intramol...

A fast perfusion system was used to apply excitatory amino acids to embryonic hippocampal neurons grown in dissociated culture and voltage clamped in the whole-cell recording configuration. Responses to quisqualic acid and DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA; a potent quisqualate-like agonist) showed rapid desensitization: at 100 microM the peak inward current dec...

The dependence on ionic strength of protonation of L-aspartic acid and its complexation withdioxouranium(VI) is reported in sodium perchlorate solution as a background salt. The measurementshave been performed at 25 ± 0.1 °C and various ionic strengths in the range 0.1 to 1.0 mol dm-3, using acombination of potentiometric and spectrophotometric techniques. The overall analysis of the present an...