Serine

serine

[′se‚rēn]

(biochemistry)

C₃H₇O₃N An amino acid obtained by hydrolysis of many proteins; a biosynthetic precursor of several metabolites, including cysteine, glycine, and choline.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Serine

 

(also, α-amino-β-hydroxypropionic acid), HOCH₂CH(NH₂)COOH, a naturally occurring amino acid. Serine exists in two optically active forms, namely, the L and D forms, and in the racemic, or DL, form. Practically all proteins contain L-serine. The proteins of silk are especially rich in serine; fibroin contains up to 16 percent, and sericin up to <0 percent. Serine was isolated from sericin in 1865 by the German chemist E. Cramer. Phosphoesters of serine also enter into the composition of proteins. Serine is a replaceable amino acid; its precursor in biosynthesis by living organisms is D-3-phosphoglyceric acid, an intermediate product of glycolysis. In cells, serine participates in the biosynthesis of glycine, sulfur-containing amino acids (methionine, cysteine), and tryptophan, as well as of ethanolamine and sphingolipids. It serves as a source for a monocarbon fragment (conversion to glycine with the participation of tetrahydrofolic acid), which plays an important role in the biosynthesis of choline and purines:

Serine + Tetrahydrofolic acid → Glycine + N₅, N₁₀-methylene-tetrahydrofolic acid

Upon the decomposition of serine in organisms, pyruvic acid is formed, which is introduced into the tricarboxylic acid cycle by means of conversion into acetyl coenzyme A. The catalytic function of a series of enzymes (chymotrypsin, trypsin, bacterial proteases, esterases, phosphorylase, phosphoglucomutase, alkaline phosphatase) derives from the reactivity of the hy-droxyl group of the serine residue, which forms part of the active site of these enzymes. Reactions of the enzymes of the serine group include the hydrolysis of peptides, amides, and the esters of carboxylic acids and the transfer of the residue of phosphoric acid. The antibiotics cycloserine and azaserine are derivatives of serine.

REFERENCE

Lehninger, A. Biokhimiia. Moscow, 1974. (Translated from English.)

E. N. SAFONOVA

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.