Difference in susceptibility of arginine-vasopressin and oxytocin to aminopeptidase activity in brain synaptic membranes
Burbach, J.P.; Wang, X.; van Ittersum, M.
Biochemical and Biophysical Research Communications 108(3): 1165-1171
1982
ISSN/ISBN: 0006-291X PMID: 7181888 Document Number: 183717
Arginine-vasopressin and oxytocin peptides which serve as putative precursors for neurotrophic fragments, were digested in the presence of the respective 14C-Tyr2- and 14C-GlyNH29-labeled nonapeptides with a purified synaptic membrane preparation of rat brain. In this preparation aminopeptidase activity predominates in the conversion of these peptides. The disappearance of intact peptide and the release of free 14C-Tyr and 14C-GlyNH2 was followed simultaneously with time by HPLC . Oxytocin was about 4 times more resistant to proteolysis than arginine-vasopressin as measured by slower disappearance of intact oxytocin, and reflected by the slower release of 14C-Tyr, but not of 14C-GlyNH2 from oxytocin. Comparison of degradation rates of structure analog showed that peptides having Ile in position 3, as oxytocin, were more resistant than analogs having Phe in position 3, as arginine-vasopressin. Arginine-vasopressin and oxytocin differ markedly in susceptibility to the aminopeptidase activity in brain synaptic membranes, and this difference resides primarily in the amino acid residue in position 3. Apparently, the difference in susceptibility may affect the pattern of neurotrophic metabolites in brain.