A System for the Study of Kallikreins

Abstract

The formation of kallidin (lysyl-bradykinin) by the action of glandular kallikreins upon plasma kininogen shows that the substrate specificity of these enzymes is very different from that of trypsin and plasma kallikrein, which yield bradykinin from the same substrate. Although one of the bonds cleaved by glandular kallikrein (Arg-Ser, at the carboxyl end of bradykinin and kallidin) is a typical trypsin substrate cleavage site, and is also cleaved by plasma kallikrein, the other site (Met-Lys, at the amino end of kallidin) is not cleaved by trypsin and plasma kallikrein. This unique second cleavage site has led to considerable work and discussion as to whether the enzyme has one or two active sites (see Fiedler and Leysath, and Prado and Araujo-Viel, this volume). In order to study glandular kallikreins more exactly and as an aid to development of specific inhibitors for glandular kallikreins, a new set of substrates has been synthesized and used for initial studies with rat urinary kallikrein (RUK).