Biochemical, Pharmacological, and Functional Aspects of Glandular Kallikreins

Kallikrein (EC 3.4.21.8) specifies those serine proteinases which liberate kinins from kininogens by limited proteolysis and have no or only little proteolytic activity on other proteins (for review, see refs. 2,3,21). Unfortunately, this definition fits two totally different groups of proteinases: the glandular, tissue or organ kallikreins on the one hand, and the plasma or serum kallikrein on the other. The two types differ (a) in physicochemical properties; (b) in the type of kinin they release (plasma kallikreins: bradykinin; glandular kallikreins: kallidin = lysylbradykinin); (c) in immunochemical properties (no cross-reactivity of the one type with antiserum directed against the other type has ever been observed); and (d) in susceptibility to inhibition by natural proteinase inhibitors. The plasma kallikrein plays an important role in the coagulation/fibrinolysis system (21). The physiological function of the glandular kallikreins is still to a large degree a matter of speculation. Glandular kallikreins are found in pancreas, salivary and sweat glands, intestines, kidney, and urine.