Serine

Serine protease: []
 * Serine** (abbreviated as **Ser** or **S**)[|[][|3][|]] is an [|amino acid] with the [|formula] [|H][|O]2[|C]CH([|N]H2)CH2OH. It is one of the [|proteinogenic amino acids]. Its [|codons] in the [|genetic code] are UCU, UCC, UCA, UCG, AGU and AGC. By virtue of the hydroxyl group, serine is classified as a polar amino acid.

This compound is one of the naturally occurring [|proteinogenic amino acids]. 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.[//[|citation needed]//] The biosynthesis of serine starts with the [|oxidation] of [|3-phosphoglycerate] to [|3-phosphohydroxypyruvate] and [|NADH]. [|Reductive amination] of this ketone followed by hydrolysis gives 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).[|[][|4][|]] This compound may also be naturally produced when UV light illuminates simple ices such as a combination of water, methanol, hydrogen cyanide, and ammonia, suggesting that it may be easily produced in cold regions of space.

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. As a constituent (residue) of proteins, its [|side chain] can undergo //O//-linked [|glycosylation], which may be functionally related to [|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.