D-amino acids in higher plants

Although there appear to be no exceptions to the rule that proteins are composed solely of the L-isomers of amino acids, D-amino acids and derivatives of them do occur rather widely in living organisms. In some cases they have well-understood functions, but in other cases their occurrence raises interesting questions. Several peptide antibiotics contain D-amino acids (1). The peptido-glycans of Gram-positive bacterial cell walls contain D-glutamic acid, D-alanine, and D-asparagine (2). D-amino acids are also found in animals, chiefly annelids and insects (3). In this paper some aspects of D-amino acids in higher plants will be reviewed.