d-AMINO ACIDS IN ANIMAL PEPTIDES

d-amino acids have been detected in a variety of peptides synthesized by animal cells. These include opiate and antimicrobial peptides from amphibian skin, neuropeptides from snail ganglia, a hormone from crustaceans, and a constituent of a spider venom. cDNA cloning has shown that at those positions where a d-amino acid is found in the end-product, a normal codon for the corresponding l-amino acid is present. This implies that the d-residues are formed from l-amino acids by a posttranslational reaction. A prototype enzyme catalyzing such a reaction has recently been isolated from the venom of the funnel web spider.