Kinetics of bond cleavages at kallidin release by tissue kallikrein: cleavage of two peptide bonds in a single enzyme-substrate complex?

The kinetics of the release of kallidin, L- and KL-chains from bovine L-kininogen by porcine tissue kallikrein were followed and individual kinetic constants for cleavage of the Met-360 and the Arg-370 bond determined. The results suggest that both these bonds in L-kininogen r are hydrolyzed "simultaneously" without appearance of a free singly-nicked intermediate. Kallidin release in the human analogous system is also compatible with such a mechanism.