ABSTRACT
The 20 amino acids incorporated in protein are known as protein amino acids, and the amino acids that are not found in proteins are known as nonprotein amino acids. More than 900 nonprotein amino acids have been identified in plants. Many of the nonprotein amino acids resemble protein amino acids and often can be considered their structural analogues (1-5). They often derive biosynthetically from protein amino acids. Some nonprotein amino acids are simple homologues of protein amino acids. Such compounds have molecular sizes and conformations that do not differ too markedly from those of the corresponding protein amino acids and so they may act as analogue molecules, sometimes mimicking the behavior of normal molecules and sometimes acting as metabolic antagonists or inhibitors.
