Not More than Three Tissue Kallikreins Identified from Organs of the Guinea Pig

The large and varied multigene families of tissue kalli-kreins of rat and mouse are considered to selectively release as many bioactive peptides. In order to deter-mine whether a similar family of enzymes is expressed in the organs of the guinea pig purification studies were performed. Tissue kallikreins from the subman-dibular gland, coagulating gland/prostate complex and the pancreas were separated by affinity chro-matography on benzamidine-Sepharose. Amino-ter-minal sequences, the patterns of hydrolysis rates of a number of peptide p-nitroanilides, inactivation rates by active site-directed irreversible inhibitors, specific kininogenase activities and types of kinin released were used to probe the identity of the isolated en-zymes. Guinea pig tissue kallikreins 1 and 2 have been re-ported previously. In the present study we have iden-tified a third type, designated tissue kallikrein 1a be-cause of its sequence similarity to kallikrein 1, which differs from the latter in the catalytic properties. The inferred occurrence of not more than two or three in-dependent tissue kallikrein genes in the guinea pig contrasts with the varied family of enzymes expressed by the large number of such genes present in rats and mice. Expression in the guinea pig (and also in humans) of only a small number of tissue kallikreins makes specific processing of a multitude of biologi-cally active peptides by such enzymes unlikely