Alanine synthesis

Alanine synthesis in muscle The synthesis and release of alanine by muscle can be considered as a safety mecha-... 

The thermodynamics of the alanine synthesis reaction are favourable if a large excess of ammonium is used. In a batch reactor the number of regenerations of... 

Arecoline is prepared from bis(2-cyanoethyl)amine (174) which is a by-product of the alanine synthesis [125] (Scheme 23). 

L-alanine Synthesis process CL 100 0.5—25 mmol L-1 Immobilised L-amino acid oxidase [125]... 

On adding acetyl-L-alanine (as the product of the synthesis reaction) to a reaction mixture as specified in Fig. 7-20 D, the measured enzyme activity rapidly decreases, indicating product inhibition. Finally the measured activity reaches negative values. A negative activity here means a negative rate of acetyl-L-alanine synthesis, that is, hydrolysis. 

Kumagai and coworkers11131 developed an enzymatic procedure to produce d-alanine from fumarate by means of aspartase (E. C. 4.3.1.1), aspartate racemase, and D-amino acid aminotransferase (Fig. 17-12). Aspartase catalyzes conversion of fumarate into L-aspartate, which is racemized to form D-aspartate. D-Amino acid aminotransferase catalyzes transamination between D-aspartate and pyruvate to produce D-alanine and oxalacetate. This 2-oxo acid is easily decarboxylated spontaneously to form pyruvate in the presence of metals. Thus, the transamination proceeds exclusively toward the direction of D-alanine synthesis, and total conversion of fumarate into D-alanine was achieved. 

Glycosynthases are classified as mutated retaining glycosidases where the active site carboxylate nucleophile has been replaced by a nonnucleophilic amino acid side chain (such as alanine). Synthesis of oligosaccharides by the glycosynthase enzymes, which do not hydrolyze the products and use inexpensive... 

FIG. 5.4 Alanine synthesis and the reoxidation of glycolytic NADH. 1, Glycolysis 2, alanine aminotransferase 3, NAD-dependent glutamate dehydrogenase 4, NADP-dependent glutamate dehydrogenase 5, malate dehydrogenase 6, malic enzyme (cytosolic). 

When alanine is a major end-product of glucose catabolism, substantial amounts of nitrogenous compounds must be available to contribute the amino group. In a number of species alanine formation is accompanied by proteolysis which would release a pool of amino acids from which the nitrogen could be derived. In G. lamblia and Trichomonas vaginalis arginine catabolism is a likely provider of nitrogen for alanine synthesis. The efflux of alanine from G. lamblia is due to an alanine antiport which is also responsible for alanine uptake and acts to maintain a balance between intracellular and extracellular alanine concentrations (36). 

The common mechanism of aspartate biosynthesis is analogous to that of alanine synthesis, as either oxaloacetate [Eq. (3)] or pyruvate [Eq. (1)] would... 

Alanine synthesis from 3-PGA in the dark. Intact BSS (50 pg chlorophyll/ml) were incubated for two minutes with the additions indicated and the reaction was started by adding 3-PGA at 30 C. At various times, the reaction was stopped by 3% HCIO4 and after neutralizing with KOH metabolites were assayed spectrophotometrically (6) in the following sequence pyruvate with lactate dehydrogenase, PEP with pyruvate kinase, 2-PGA with enolase and 3-PGA with phosphoglycerate mutase. Alanine was assayed according to ref(7). 

In the experiment of table 2, the components of the incubation of BSS were varied. The results show that for the synthesis of alanine 3-PGA could be replaced by 2-PGA or PEP. When ADP or glutamate were omitted, 2-PGA and PEP were also produced, as to be expected, but there was not alanine synthesis observed. The formation of pyruvate from PEP in the absence of ADP, occurring at a low rate, reflects a PEP phosphatase activity of unknown origin. The results of table 2 confirm that the formation of alanine from 3-PGA in BSS proceeds via the glycolytic sequence. 

In some microorganisms, ammonia assimilation may also occur by alanine synthesis, catalysed by alanine dehydrogenase (EC 1.4.1.1). 

Antimicrobial action. The action of propionic acid is directed mainly against moulds. Yeasts are likewise inhibited, and so also are some gram-negative bacteria. Some yeasts (e. g. torula species), are capable of utilizing propionic acid in their metabolism. Inhibition of E. coli may be reversed with addition of B-alanine, indieating that propionates interferes with B-alanine synthesis (Doores, 1993). In general the action of propionic acid is weak in comparison with other preservatives from the organic acid type (Heseltine, 1955). 

From the above results we may conclude that the serosal border is the site of L-alanine synthesis, since radioactive L-alanine appearing in the serosal saline is diluted by non-radioactive L-alanine. This mechanism must be located very near the serosal border or in the membrane itself, because the specific activity of L-alanine in the intracellular fluid is equal to that in the mucosal saline. 

The synthesis of alanine in chloroplasts has been questioned due to the apparent lack of an appropriate aminotransferase in these oiganelles (Biek-mann and Feierabend, 1982). Contrasting conclusions can be drawn fi-om the results of other studies. For example, alanine synthesis from [2- ]pyruvate or [ C]bicarbonate has been demonstrated in purified spinach chloroplasts (Schulze-Siebert et ai, 1984). Since the rate of alanine synthesis from pyruvate was significantly enhanced upon rupture of the chloroplasts, the possibility that alanine synthesis was due to contaminants of the plastid preparations is diminished. These and other results noted above suggest that appropriate aminotransferases are widely distributed within plant cells. The availability of an... 

L-alanine synthesis. Similar difference in terms of substrate binding and product release was observed in reactions by other amino acid dehydrogenases such as GluDH and LeuDH... 

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