Substrate specificity of two kallikrein family gene products isolated from the rat submaxillary gland.

Two proteinases which belong to the tissue kallikrein family were purified from rat submaxillary glands. These proteinases correspond to the products of the RSKG-7 and the rGK8 genes, as shown by the comparison of their partial amino-acid sequence with that deduced from nucleotide sequences. These two proteinases, kallikrein k7 and kallikrein k8, exhibit a marked preference for cleavage after arginyl residues. However, their overall specificities towards synthetic fluorogenic substrates differ significantly from each other and from that of true tissue kallikrein. Kallikrein k7 is strongly inhibited by soybean trypsin inhibitor, whereas kallikrein k8 is not. These data, demonstrating the individual specificity of these kallikrein-like proteinases, suggest that they could be involved in the processing of peptides other than kinins.