Difference in susceptibility of arginine-vasopressin and oxytocin to aminopeptidase activity in brain synaptic membranes |
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Authors: | J.Peter H. Burbach Xinchang Wang Marjanne van Ittersum |
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Affiliation: | Rudolf Magnus Institute for Pharmacology Medical Faculty, University of Utrecht Vondellaan 6, 3521 GD Utrecht, The Netherlands |
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Abstract: | Arginine-vasopressin and oxytocin, peptides which serve as putative precursors for neurotrophic fragments, were digested in the presence of the respective 14C-Tyr2- and 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 four 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 analogues showed that peptides having Ile in position 3, as oxytocin, were more resistant than analogues having Phe in position 3, as arginine-vasopressin. The data demonstrate that arginine-vasopressin and oxytocin differ markedly in susceptibility to the aminopeptidase activity in brain synaptic membranes, and indicate that this difference resides primarily in the amino acid residue in position 3. It is suggested that the difference in susceptibility may affect the pattern of neurotrophic metabolites in brain. |
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Keywords: | AVP arginine-vasopressin OXT oxytocin LVP lysine-vasopressin AVT arginine-vasotocin OXP oxypressin PA pressinamide TA tocinamide HPLC high-pressure liquid chromatography |
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