Aspartic acid occurrence

Trypsin cleaves adjacent to arginine and lysine, but has a preference for arginine, particularly at high pH values. In the sequences Arg-X or Lys-X, cleavage is inhibited if there is a proline residue at position X. Cleavage is also inhibited by glutamic acid and aspartic acid, and by the occurrence of additional arginine or lysine residues. 

Still and co-w orkers were unable to secure the oxidation of L-aspartic acid with rabbit liver cyclophorase preparations, although they discovered the occurrence of an enzyme in these preparations capable of oxidizing D-aspartate. 

Homoserine also has been detected in filtrates of liver preparations incubated with methionine. Cantoni provisionally identified homoserine as a product of the acid hydrolysis of active methionine (S-adeno-sylmethionine). Beyond homoserine, the postulated reactions 2 and 3 are still more speculative. It might be presumed that homoserine is oxidized to aspartic acid, in analogy to the observations on the catabolism of lysine, in which the analogous a-amino adipic acid is an intermediate. If aspartic acid is formed, the subsequent reaction sequence is readily apparent. Evidence favorable to the proposed reaction pathway is the finding of Marshall and Friedberg, of the occurrence of a small amount of fumaric acid, labeled in the methine carbons, from the livers of mice injected with DL-methionine-2-C. ... 

The oxidation of tryptophan with periodate under acid, neutral and alkaline conditions has been studied (18, 221, 326). Yields of isolated products were low due to occurrence of deamination and tar formation (78). Products detected (8% yield) include formylkynurenine under neutral conditions and dioxindolylalanine under acid conditions. Traces of serine and aspartic acid were also detected. Oxidation in the presence of ammonia gave the quinazoline (56) previously identified (338) as a photooxidation product of tryptophan. By contrast, indole-3-... 

Pantothenic acid is of ubiquitous occurrence in nature, where it is synthesized by most microorganisms and plants fi-om pantoic acid (D-2,4-dihydroxy-3,3-dimethylbutyric acid) derived from L-vafine, and p-alanine derived from L-aspartate. Addition of cysteamine at the C-terminal end and phosphorylation at C4 of pantoic acid forms 4 -phosphopantetheine, which serves as a covalently attached prosthetic group of acyl carrier proteins, and, when attached... 

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