Alanine, biosynthesis

Kanamori, K., Legerton, T.L., Weiss, R.L., Roberts, J.D. (1982). Effect of the nitrogen source on glutamine and alanine biosynthesis in Neurospora crassa. J. Biol. Chem. 257,14168-14172. 

L Glutamic acid is not an essential ammo acid It need not be present m the diet because animals can biosynthesize it from sources of a ketoglutaric acid It is however a key intermediate m the biosynthesis of other ammo acids by a process known as transamination L Alanine for example is formed from pyruvic acid by transamination from L glutamic acid... 

Aspartic acid decarboxylase cataly2es the decarboxylation of asparatic acid to yield P-alanine (10), a precursor for the biosynthesis of pantothenic acid (67). FiaaHy, (R)-pantothenic acid is obtaiaed by coupling P-alaniae (10) with (R)-pantoate (22) ia the presence of pantothenate synthetase ... 

Thymine, electrostatic potential map of, 1104 structure of, 1101 Thyroxine, biosynthesis of, 551 structure of. 1020 TIme-of-flight (TOP) mass spectrometry, 417-418 Titration curve, alanine, 1023 TMS, see Tetramethylsilane see Trimethylsilyl ether Tollens reagent, 701 Tollens test, 992... 

Pyridoxamine phosphate serves as a coenzyme of transaminases, e.g., lysyl oxidase (collagen biosynthesis), serine hydroxymethyl transferase (Cl-metabolism), S-aminolevulinate synthase (porphyrin biosynthesis), glycogen phosphoiylase (mobilization of glycogen), aspartate aminotransferase (transamination), alanine aminotransferase (transamination), kynureninase (biosynthesis of niacin), glutamate decarboxylase (biosynthesis of GABA), tyrosine decarboxylase (biosynthesis of tyramine), serine dehydratase ((3-elimination), cystathionine 3-synthase (metabolism of methionine), and cystathionine y-lyase (y-elimination). 

The P-alanyl dipeptides carnosine and anserine (A -methylcarnosine) (Figure 31-2) activate myosin ATPase, chelate copper, and enhance copper uptake. P-Alanyl-imidazole buffers the pH of anaerobically contracting skeletal muscle. Biosynthesis of carnosine is catalyzed by carnosine synthetase in a two-stage reaction that involves initial formation of an enzyme-bound acyl-adenylate of P-alanine and subsequent transfer of the P-alanyl moiety to L-histidine. 

Fig. 8.1 Biosynthesis of peptidoglycan. The large circles represent A -acetylglucosamine orN-acetylmuramic acid to the latter is linked initially a pentapeptide chain comprising L-alanine, D-glutamic acid and meso-diaminopiraelic acid (small circles) terminating in two D-alanine residues (small, darker circles). The lipid molecule is undecaprenyl phosphate. In the initial (cytoplasm) stage where inhibition by the antibiotic D-cycloserine is shown, two molecules of Dalanine (small circles) are converted by an isomerase to the D-forms (small, darker circles), alter which a ligase joins the two D-alanines together to produce a D-alanyl-D-alanine dipeptide.

Another enzyme, cysteine desulfurase, converts L-cysteine to L-alanine and a sulfane sulfur - a chain of divalent sulfur atoms. A protein-bound cysteine persulfide is formed on a conserved cysteine residue. Such enzymes have important roles in the biosynthesis of Fe-S clusters and sulfur-containing cofactors.9... 

Sterol biosynthesis Bile acid biosynthesis C2rSteroid hormone metabolism Androgen and estrogen metabolism Nucleotide Metabolism Purine metabolism Pyrimidine metabolism Nucleotide sugar metabolism Amino sugar metabolism Amino Acid Metabolism Glutamate metabolism Alanine and aspartate metabolism Glycine, serine, and threonine metabolism... 

D-Arginine and D-ornithine metabolism D-Alanine metabolism Glutathione metabolism Alkaloid biosynthesis I Alkaloid biosynthesis II Metabolism of Complex Carbohydrates Starch and sucrose metabolism Biosynthesis and degradation of glycoprotein... 

L. J. Reitzer, Ammonia Assimilation and the Biosynthesis of Glutamine, Glutamate, Aspartate, Asparagine, L-alanine, and D-alanine. In Escherichia coll and Salmonella, Cellular and Molecular Biology F. C. Neidhardt, Ed. ASM Press Washington, DC, 1996 Vol. 1, pp 391 07. 

Cycloserine (Fig- 4) is produced by several species of Streptomyces. One of the basic glycosyl components of the bacterial cell wall, n-acetyl-muramic acid (the product of Mur A and MurB), is modified by the addition of the first three amino acids sequentially by MurC, MurD and MurE enzymes. A dipeptide, D-alanyl-D-alanine is then added to make the pentapeptide. In bacteria, L-alanine is the native form and it is converted to D-alanine form by alanine racemase (Air). Two D-alanines are joined by D-ala-D-ala ligase (DdlA) to synthesize the dipeptide. Cycloserine resembles the substrate for Air and Ddl and inhibits their respective reactions in stage I of the peptidoglycan biosynthesis (Fig. 2). 

Fluoro amino acids have been incorporated into peptides, in order to ease the transport or reduce the systemic toxicity. Thus, trifluoroalanine, a powerful inhibitor of alanine racemase, is an essential enzyme for the biosynthesis of the cell wall of bacteria. It has a low antibiotic activity because of its very poor transport. In order to facilitate this transport, the amino acid has been incorporated into a peptide. This delivery allows a reduction of the doses, and thus the toxicity of the treatment is lowered.3-FIuorophenylaIanine (3-F-Phe) is a substrate of phenylalanine hydroxylase, which transforms it into 3-F-Tyr. 3-F-Tyr has a high toxicity for animals, due to its ultimate metabolization into fluorocitrate, a powerful inhibitor of the Krebs cycle (cf. Chapter 7). 3-F-Phe has a low toxicicity toward fungus cells, but when delivered as a tripeptide 3-F-Phe becomes an efficient inhibitor of the growth of Candida albicans. This tripeptide goes into the cell by means of the active transport system of peptides, where the peptidases set free the 3-F-Phe. ... 

During the biosynthesis of the cell wall, the muropeptide is formed from acetylmuramyl-pentapeptide, which terminates in a D-alanyl-D-alanine. The synthesis of this precursor is inhibited by the antibiotic cycloserine (9.36), a compound produced by many Streptomyces fungi but which is not used clinically. During the crosslinking of the pen-tapeptide precursor, the terminal fifth alanine must be split off by a transpeptidase enzyme. This last reaction in cell wall synthesis is inhibited by the p-lactam antibiotics. 

Purification of some enzymes participating in the biosynthesis of glycopeptide cell-wall precursors has also been achieved. Examples include preparation of the enzymes necessary for synthesis of the enol ether 38 (see Section 11,6, p. 328),152-153-450 reduction of the enol ether to the muramic acid derivative,152-450,451 and the addition to the latter of amino acids452-456 or the dipeptide D-alanyl-D-alanine.160-457-458... 

Muscle activity involves processes such as aerobic and anaerobic glycolysis and is therefore accompanied by an increased pyruvate production. Consequently, the pyruvate transamination product alanine will be increased after exercise. Heavy exercise may be associated with an increased need of creatine biosynthesis from arginine. Ornithine is a by-product of this pathway and may be increased under these conditions. 

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