A regulatory relationship in Bacillus subtilis between histidine and the synthesis of tryptophan exemplifies “metabolic interlock,” a phenomenon of regulatory interactions exerted between biochemical pathways. The enzymatic basis for the histidine-tryptophan relationship was examined. Histidine activates anthranilate synthetase by increasing the apparent value of VmSx. Hence, histidine antagoni...

NMR titration curves are reported for the 4 histidine residues of ribonuclease A in sodium acetate and for ribonuclease S in sodium acetate, phosphate, and sulfate solutions. Evidence is presented that the imidazole side chain of histidine residue 48 undergoes a conformational change, probably also involving the carboxyl side chain of aspartic acid residue 14. This group is considered to be res...

Histidine (His) is one of the standard amino acids in proteins, and plays a critical role in plant growth and development. The chemical properties of the imidazole side group allow His to participate in acid-base catalysis, and in the co-ordination of metal ions. Despite the biological importance of this molecule, His biosynthesis has been somewhat neglected in plants, in stark contrast to micr...

The requirement of Lactobacillus casei and Lactobacillus arabinosus for purine bases is increased when these organisms are grown in the absence of histidine. These and related observations were interpreted to mean that purine bases serve as precursors of histidine for these organisms.1 Recent studies by Levy and Coon2'3 have established that in yeast the imidazole ring of purine bases does not ...

The pathway for histidine biosynthesis in Salmonella typhimurium, elucidated largely through the efforts of Dr. B. N. Ames and co-workers,1-5 is shown in Figure 1. The figure also shows that portion of the pathway for purine biosynthesis which involves the further metabolism of 4-amino-5-imidazole carboxamide ribonucleotide (phosphoribosyl-AIC).6 Dr. Phillip Hartman and his colleagues have show...

In Arabidopsis thaliana, blocking histidine biosynthesis with a specific inhibitor of imidazoleglycerol-phosphate dehydratase caused increased expression of eight genes involved in the biosynthesis of aromatic amino acids, histidine, lysine, and purines. A decrease in expression of glutamine synthetase was also observed. Addition of histidine eliminated the gene-regulating effects of the inhibi...

A group of 28 uraemic patients on dialysis treatment were given daily supplements of histidine by mouth. Plasma amino-acid concentration, plasma iron, serum transferrin, packed cell volume, and reticulocyte count were all measured before and after two months of histidine supplementation. The treatment raised the plasma histidine concentration and at the same time there was a rise in transferrin...

in this study, the effect of the secondary structure of the protein on the acid strength of three structures of random (r), alpha helix (α) and beta sheet (b) were investigated theoretically. these structures are related to the cationic amino acids of histidine and lysine in the polypeptide chain of eight-glycine residue. computational methods at the hf, b3lyp, x3lyp and m05-2x levels in the ga...

We demonstrate spectroscopic imaging using a compact ultra-broadband terahertz semiconductor source with high-power, mid-infrared quantum cascade laser. The electrically pumped monolithic is based on intra-cavity difference-frequency generation and can be designed to achieve an multi-mode emission spectrum extending from 1–4 THz without any external optical setup. Spectroscopic was performed th...