Not more than three tissue kallikreins identified from organs of the guinea pig

The large and varied multigene families of tissue kallikreins of rat and mo use are considered to selectively release as many bioactive peptides. In or der to determine whether a similar family of enzymes is expressed in the or gans of the guinea pig purification studies were performed. Tissue kallikre ins from the submandibular gland, coagulating gland/prostate complex and th e pancreas were separated by affinity chromatography on benzamidine-Sepharo se. Amino-terminal sequences, the patterns of hydrolysis rates of a number of peptide p-nitroanilides, inactivation rates by active site-directed irre versible inhibitors, specific kininogenase activities and types of kinin re leased were used to probe the identity of the isolated enzymes. Guinea pig tissue kallikreins 1 and 2 have been reported previously. In the present study we have identified a third type, designated tissue kallikrei n la because of its sequence similarity to kallikrein 1, which differs from the latter in the catalytic properties. The inferred occurrence of not mor e than two or three independent tissue kallikrein genes in the guinea pig c ontrasts 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 als o in humans) of only a small number of tissue kallikreins makes specific pr ocessing of a multitude of biologically active peptides by such enzymes unl ikely.