Interaction of chymotrypsin with carbetocin ([1-deamino-1-monocarba-2-O-methyltyrosine]-oxytocin).

The results of the present study describe the course of reaction and the products following chymotrypsin treatment of the oxytocin analogue carbetocin ([1-deamino-1-monocarba-2-O-methyltyrosine]-oxytocin). The metabolites were analyzed and identified through TLC, HPLC and mass spectrometry. The main product emerging after treatment of carbetocin with chymotrypsin is 9-desglycineamide carbetocin indicating preferential hydrolysis of the peptide bond between leucine at position 8 and carboxyterminal glycineamide. At the same time the stability of the bond between tyrosine at position 2 and isoleucine at position 3 appears significantly enhanced through the alkylation of the hydroxyl group of tyrosine.