Hydrolysis of various bioactive peptides by goat brain dipeptidylpeptidase-III homologue

DPP-III from goat brain was purified to apparent electrophoretic homogeneity which showed several characteristics similar to other reported DPP-IIIs although it possesses dissimilar molecular weight and different inhibition behavior. Thin layer chromatographic studies with goat brain DPP-III revealed that it hydrolyses Leu-enkephalin (Tyr-Gly-Gly-Phe-Leu) at the Gly-Gly bond producing Tyr-Gly and Gly-Phe-Leu with no further degradation of liberated tripeptide. (Ala)(4) is hydrolyzed to dialanine whereas trialanine is not cleaved. ACTH, angiotensin II and III were also hydrolyzed whereas angiotensin I was not. It was concluded that the enzyme requires at least a tetrapeptide to act and that it removes a dipeptidyl moiety from the NH(2)-terminus of the studied peptides. Goat brain DPP-III may be involved in the metabolism of very important bioactive peptides such as enkephalins and angiotensins.