'Serine' (
IPA ) is an
organic compound with the
formula HO2CCH(
NH
2)CH
2OH. It is one of the 20 naturally occurring
proteinogenic amino acids. Its three letter code is Ser, its one letter code is S, and its
codons are UCU, UCC, UCA, UCG, AGU and AGC.
[1] Only the L-
stereoisomer appears naturally in proteins. It is not essential to the human diet, since it is synthesized in the body from other
metabolites, including
glycine. Serine was first obtained from
silk protein, a particularly rich source, in 1865. Its name is derived from the
Latin for silk, ''sericum''. Serine's structure was established in 1902. The hydroxyl group attached makes it a polar amino acid.
Biosynthesis
The synthesis of serine starts with the
oxidation of
3-phosphoglycerate forming
3-phosphohydroxypyruvate and
NADH.
Reductive amination of this ketone followed by hydrolysis affords serine.
Serine hydroxymethyltransferase catalyzes the reversible, simultaneous conversions of L-serine to
glycine (retro-aldol cleavage) and
5,6,7,8-tetrahydrofolate to
5,10-methylenetetrahydrofolate (hydrolysis).
[2]
Function
Metabolic
Serine is important in
metabolism in that it participates in the
biosynthesis of
purines and
pyrimidines. It is also the precursor to several amino acids, including
glycine,
cysteine,
tryptophan (in bacteria). It is also the precursor to numerous of other metabolites, including
sphingolipids. Serine is also a precursor to
folate which is the principal donor of one carbon fragments in biosynthesis.
Structural
Serine plays an important role in the catalytic function of many
enzymes. It has been shown to occur in the active sites of
chymotrypsin,
trypsin, 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
acetylcholine as soon as it performs its function, dangerously high levels of this
neurotransmitter build up, quickly resulting in
convulsions and
death.
As a constituent (residue) of proteins, its
side chain can undergo O-linked
glycosylation. This might be important in explaining some of the devastating consequences of
diabetes. It is one of three amino acid residues that are commonly
phosphorylated by
kinases during
cell signaling in
eukaryotes. Phosphorylated serine residues are often referred to as 'phosphoserine'.
Serine proteases are a common type of protease.
Signaling
D-serine, synthesized by
serine racemase from L-serine, serves as a neuronal signaling molecule by activating
NMDA receptors in the brain.
Chemical Synthesis
Serine is prepared from methyl acrylate.
[3]
See also
★ Serine aggregation properties in
Serine octamer clusters
References
1. Nomenclature and Symbolism for Amino Acids and Peptides IUPAC-IUBMB Joint Commission on Biochemical Nomenclature
2. Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.
3. Carter, H. E.; West, H. D. “dl-Serine” Organic Syntheses, Collected Volume 3, p.774 (1955). http://www.orgsyn.org/orgsyn/pdfs/CV3P0774.pdf
External links
★
Computational Chemistry Wiki
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