Serine (abbreviated as Ser or S) is an organic compound with the formula HO2CCH(NH2)CH2OH. Occurrence It is one of the naturally occurring proteinogenic amino acids. Its codons are UCU, UCC, UCA, UCG, AGU and AGC. Only the L-stereoisomer appears naturally in proteins. It isn't essential to the human diet, since it's 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 Lat… (More on Serine)