Proteolytic conversion of arginine-vasotocin by synaptic membranes from rat and chicken brain

This paper reports studies on the biotransformation of the nonapeptide arginine-vasotocin (AVT) by both rat and chicken brain synaptic membranes. The fragments which were formed during digestion of AVT1-9, were isolated by high pressure liquid chromatography (HPLC) and chemically characterized by amino acid composition, NH2-terminal amino acid residues and the presence of 14C-radioactivity of the residue glycinamide-9. The major peptide fragments of AVT were: (formula; see text) Time course experiments showed the precursor-product interrelationships between these peptides. The results demonstrate that the conversion of AVT by synaptic membranes involves primarily the action of aminopeptidase activity. Comparison between membrane fractions from rat and chicken brain showed that AVT is converted by a similar proteolytic mechanism in chicken brain, but that differences in activity of the aminopeptidase exist. The results are discussed in view of the concept that AVT serves as precursor for neuropeptides with differential activities in non-mammalian vertebrates.