Comparative study of the action of bovine duodenal proteinases (duodenases) on polypeptide substrates

A comparative study of substrate specificity of bovine duodenal proteinases -chymotrypsin-like duodenase (ChlD) and dual-specificity duodenase (dsD)-wa s carried out using oligopeptide substrates (human proinsulin, glucagon, me littin, angiotensinogen fragment 1-14). ChlD displayed mainly chymotrypsin- like properties towards these substrates, hydrolyzing peptide bonds carboxy -terminally to bulky aliphatic or aromatic residues. In melittin, ChlD addi tionally cleaved peptide bonds after Thr and Ser residues. Dual-specificity duodenase (dsD) significantly restricted its specificity to only trypsin-l ike or only chymotrypsin-like or displayed full activity, combining both sp ecificities, depending on substrate. Both ChlD and dsD efficiently hydrolyz ed a single peptide bond (Phe8-His9) in angiotensinogen fragment 1-14. The kinetic parameters of angiotensinogen fragment 1-14 cleavage by ChlD and ds D were determined (k(cat)/K-m = 80,500 M-1.sec(-1) for ChlD and 103,000 M-1 . sec(-1) for dsD).