Present in germinating peas, Jack bean seeds (Canavalia ensiformis) and the seedlings of many leguminous plants Homoserine is a more reactive variant of the amino acid serine. In this variant, the hydroxyl side chain contains an additional CH2 group which brings the hydroxyl group closer to its own carboxyl group, allowing it to chemically react to form a five-membered ring. This occurs at the point that amino acids normally join to their neighbours in a peptide bond.; Homoserine is therefore unsuitable for forming proteins and has been eliminated from the repertoire of amino acids used by living things.; Homoserine is the final product on the C-terminal end of the N-terminal fragment following a cyanogen bromide cleavage. (wikipedia); Homoserine is an intermediate in the biosynthesis of three essential amino acids: methionine, threonine (an isomer of homoserine), and isoleucine. It forms by two reductions of aspartic acid via the intermediacy of aspartate semialdehyde.; Homoserine is an ?-amino acid with the chemical formula HO2CCH(NH2)CH2CH2OH. L-Homoserine is not one of the common amino acids encoded by DNA. It differs from the proteinogenic amino acid serine by insertion of an additional methylene group. Homoserine, or its lactone form, is the product of a cyanogen bromide cleavage of a peptide by degradation of methionine.