Degradation of ACTH/MSH(4–10) and its synthetic analog semax by rat serum enzymes: An inhibitor study

Degradation of the behaviorally active peptide ACTH/MSH(4–10) and its synthetic analog semax was studied in serum in the presence of several specific peptidase inhibitors. Bestatin and puromycin were used to inhibit aminopeptidase activity, lisinopril for angiotensin-converting enzyme, phosphoramidon for neutral endopeptidase 24.11, and Z-Pro-prolinal for prolyl endopeptidase. Bestatin inhibited up to 66%, puromycin about 33%, and lisinopril about 15% of total degrading activity against both ACTH/MSH(4–10) and semax. Involvement of neutral endopeptidase and prolyl endopeptidase in hydrolysis of the two peptides was less definitive. These studies showed that aminopeptidases and angiotensin-converting enzyme are responsible for the major part of the hydrolysis of ACTH/MSH(4–10) and semax in rat serum.