serine

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serine

(sĕr`ēn), organic compound, one of the 20 amino acidsamino acid
, any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins.
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 commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein. It is not essential to the human diet, since it can be synthesized in the body from other metabolites, including glycineglycine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Glycine is the only one of these amino acids that is not optically active, i.e., it does not have d- and
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. Serine is important in metabolism in that it participates in the biosynthesis of purinespurine,
type of organic base found in the nucleotides and nucleic acids of plant and animal tissue. The German chemist Emil Fischer did much of the basic work on purines and introduced the term into the chemical literature in the early 20th cent.
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 and pyrimidinespyrimidine
, type of organic base found in certain coenzymes and in the nucleic acids of plant and animal tissue. The three major pyrimidines of almost universal distribution in living systems are cytosine, thymine, and uracil.
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, cysteinecysteine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer participates in the biosynthesis of mammalian protein.
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, tryptophantryptophan
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein.
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 (in bacteria), and a large number of other metabolites. When incorporated into the structure of enzymes, serine often plays an important role in their catalytic function. It has been shown to occur in the active sites of chymotrypsinchymotrypsin
, proteolytic, or protein-digesting, enzyme active in the mammalian intestinal tract. It catalyzes the hydrolysis of proteins, degrading them into smaller molecules called peptides. Peptides are further split into free amino acids.
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, trypsintrypsin,
enzyme that acts to degrade protein; it is often referred to as a proteolytic enzyme, or proteinase. Trypsin is one of the three principal digestive proteinases, the other two being pepsin and chymotrypsin.
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, and many other enzymes. The so-called nerve gases and many substances used in insecticides have been shown to act by combining with a residue of serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Without the esterase activity that usually destroys acetylcholineacetylcholine
, a small organic molecule liberated at nerve endings as a neurotransmitter. It is particularly important in the stimulation of muscle tissue. The transmission of an impulse to the end of the nerve causes it to release neurotransmitter molecules onto the surface of
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 as soon as it performs its function, dangerously high levels of this neurotransmitter build up, quickly resulting in convulsions and death. Serine was first obtained from silk protein, a particularly rich source, in 1865; its structure was established in 1902.

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

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.
References in periodicals archive ?
Despite evidence of benefit in multiple published clinical studies of non-deuterated D-serine in the treatment of schizophrenia, its use has been limited due to renal safety concerns.
Here, we describe evidence that aged microglia can promote D-serine dysregulation in the CNS and discuss how the imbalance between D-serine and other regulatory mechanisms can result in glutamate and D-serine-mediated impairment of synaptic plasticity and neurodegeneration, which can result in cognitive impairment.
Although some clinical trials show that daily administration of a large quantity of exogenous glycine or D-serine alone, as well as partial coagonists D-cycloserine or using these coagonists as an adjunct to atypical antipsychotic treatment, could result in an improvement of cognitive function and attenuate negative symptoms and positive symptoms in schizophrenia patients [3,67,68], other clinical trials had not produced positive outcomes; typically efficacy was seen in small trials while no efficacy was reported in larger trials [69, 70].
Embryonic development and postnatal changes in free D-aspartate and D-serine in the human prefrontal cortex.
The new study strongly suggested that D-serine, produced in the female sexual organs might have a role in guiding pollen tubes to their final target.
Metabolism and functional roles of endogenous D-serine in mammalian brains.
Serine racemase: a glial enzyme synthesizing D-serine to regulate glutamate-N-methyl-D-aspartate neurotransmission.
In individuals treated in the crossover study with both CTP-692 and D-serine, CTP-692 was found to have increased plasma exposure compared to D-serine.
Concert Pharmaceuticals has initiated an additional trial in the Phase 1 program evaluating CTP-692, a novel deuterium-modified form of D-serine being developed as an adjunctive treatment for schizophrenia.
Astrocytes participate in the modulation of synaptic transmission as well as in LTP through the release of glutamate and D-Serine in a [Ca.sup.2+]-dependent manner [22, 23].