Amino acid inhibition

In the case of hyperphenylalaninaemia, which occurs ia phenylketonuria because of a congenital absence of phenylalanine hydroxylase, the observed phenylalanine inhibition of proteia synthesis may result from competition between T.-phenylalanine and L-methionine for methionyl-/RNA. Patients sufferiag from maple symp urine disease, an inborn lack of branched chain oxo acid decarboxylase, are mentally retarded unless the condition is treated early enough. It is possible that the high level of branched-chain amino acids inhibits uptake of L-tryptophan and L-tyrosiae iato the brain. Brain iajury of mice within ten days after thek bkth was reported as a result of hypodermic kijections of monosodium glutamate (MSG) (0.5—4 g/kg). However, the FDA concluded that MSG is a safe kigredient, because mice are bom with underdeveloped brains regardless of MSG kijections (106). 

Enterobacter aerogenes, B. subtilis, P. fluorescens, and Serratia marces-cens produce acetoin by decarboxylation of a-acetolactate. However, yeasts and E. coli form acetoin from the acetaldehyde-TPP complex and free acetaldehyde (Rodopulo et al 1976). These organisms do not decarboxylate a-acetolactate, but use it to produce valine and pantothenic acid. In lactic acid bacteria, a-acetolactate is not used for valine or pantothenic acid synthesis, since these substances are required for growth (Law et al. 1976B Reiter and Oram 1962). In those microorganisms which can synthesize valine, this amino acid inhibits a-acetolactate synthesis (Rodopulo et al 1976). 

Seglen PO, Gordon PB, Poli A. Amino acid inhibition of autophagic/lysosomal pathway of protein degradation in isolated rat hepatocytes. Biochim Biophys Acta 1980 630 103-118. 

Elastin is a macromolecule synthesized as a 70,000 single peptide chain, termed tropoelastin and secreted into the extracellular matrix where it is rapidly crosslinked to form mature elastin. The carboxy-terminal end of elastin is highly conserved with the sequence Gly-Gly-Ala-Cys-Leu-Gly-Leu-Ala-Cys-Gly-Arg-Lys-Arg-Lys. The two Cys residues that form disulfide crosslinks are found in this region as well as a positively charged pocket of residues that is believed to be the site of interaction with microfibrillar protein residues. Hydrophobic alanine-rich sequences are known to form a helices in elastin these sequences are found near lysine residues that form crosslinks between two or more chains. Alanine residues not adjacent to lysine residues found near proline and other bulky hydrophobic amino acids inhibit a helix formation. Additional evidence exists for (3 structures and 3 turns within elastin thereby giving an overall model of the molecule that contains helical stiff segments connected by flexible segments. 

From the viewpoint of polylactic acid and polyglycolic acid, byproducts of which are chemicals naturally present in body, the development of poly(amino acids) is genuine. However, the antigenic nature of the poly(amino acids) that contain three or more amino acids inhibits their widespread use. Besides, the cleavage of the amide bond depends on enzymes, resulting in poor in vivo controlled release. Poly(amino acids) have been used mainly to deliver drugs from implants in animals. 

Ql. Quigley, J. T., and Muraschi, T. F., Amino-acid inhibition of copper proteinate formation. J. Biol. Chem. 168, 463-467 (1945). 

All three must be inhibited before production of the intermediate ceases completely. In addition, each of the amino acids inhibits the first enzyme on its branch line away from aspartate-semialdehyde, so ensuring that the decrease in concentration of the metabolite affects only the production of the inhibiting amino acid. This is an example of control by enzyme multiplicity, although the individual inhibitions are brought about by the type of allosteric processes that have already been described. 

Schott, C. A., Vetrovsky, P., and Stoclet, J. C. (1993b). Cationic amino acids inhibit the effects of L-arginine in rat aorta exposed to lipopolysaccharide. Eur.J. Pharmacol. 236,155-157. 

Harmata AJ, et al. D-amino acid inhibits biofihn but not new bone formation in an ovine model. Clin Orthop Relat Res 2015 473(12) 3951-61. 

D-Amino acids may have other effects in nephrocytomegaly, beyond influencing release of LAL. Soy protein, the most easily racemized of the four proteins studied, is more cytotoxic than lac-talbumin (Karayannis et al., 1979), the least racemized. If, as postulated, D-amino acids inhibit release of LAL, then lactalbumin would be expected to yield more free LAL than soy protein. These considerations suggest that proteolytic release of LAL may be influenced by both the presence and location of D-amino acid residues along a polypeptide chain. 

The course of enzymatic hydrolysis of arginine has been found to follow Michaelis-Menten kinetics. Competitive inhibition of arginase is effected by ornithine and lysine, but most other a-amino acids inhibit non-com-petitively. Arginase is activated by Co++, Mn++, or Ni++. The characteristics of this activation has led Hellerman to propose that the role of the activating ion is to form coordinate bonds with both substrate and en zyme. Smith has proposed a similar mechanism operating in metal-activated peptidases. 

The dehydrative deamination of serine and threonine by E. coli has been studied by several groups of investigators 216-221). The question as to whether the two substrates are attacked by separate enzymes has not been completely resolved. The partially purified preparation used by Wood and Gunsalus 216) in their studies behaved as a single enzyme and was active with both L-serine and L-threonine. The D-isomer of either amino acid inhibited deamination approximately 50%. Cysteine was found to be inactive with this enzyme. The enzyme preparation was resolved and shown to require AMP and reduced glutathione for reactivation. 

Muscle protein breakdown is a more complex and less smdied side of the equation. It has been shown that provision of amino acids inhibits muscle PB, 42-45 but not as robustly as they stimulate muscle PS. This would make sense in protein sparing because the increased extracellualar amino acids may act as a signal that amino adds are available thus PB is not needed to provide additional amino acids. However, many of the experiments showing this effect were either in vitro, conducted in nonhuman models, or conducted in individuals in extreme catabolic states such as bum victims.22 Data regarding the control of muscle PB are equivocal, with some suggesting that in nondiseased human subjects, infusion or ingestion of amino acids... 

Glyphosate Amino acid Inhibition of EPSP synthase Inhibition of amino acid synthesis 1974 Pre- and postemergence Nonselective Grasses, broadleaf weeds, 550-4500... 

Amino acid Inhibition of EPSP synthase Glyphosate 15 14 29... 

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