MSH: Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.,CSP: organic acid containing one or more amino groups, especially any of a group that make up proteins and are important to living cells; those that are nonessential can be synthesized by the body while essential acids must be obtained through the diet; there are also several important amino acids, such as the neurotransmitter g-aminobutyric acid, that have no relation to proteins.,NCI: One of several molecules that join together to form proteins. There are 20 common amino acids found in proteins.,NCI: Any organic compounds containing amino (-NH2) and carboxyl (-COOH) groups. In biochemistry, used to refer to the twenty-plus L-alpha-amino acids found in proteins.