Functional diversity of proteinases encoded by genes of the rat tissue kallikrein family.

A group of proteinases closely related to tissue kallikrein was purified from the rat submandibular gland. Physicochemical characterization of these proteinases, including amino terminal sequencing, allowed correlation with the genes of the rat kallikrein family. In spite of their similar structure, these proteinases have different substrate specificities and different susceptibilities to inhibitors which suggest that they do not share the same biological function. Kallikrein-like proteinases also have restricted specificities that are probably related to their extended substrate binding site. This makes them good candidates for processing inactive protein or peptide precursors into biologically active peptides. A general approach to identifying the putative biological substrates of individual proteinases based on analysis of the specific cleavage of synthetic and natural peptide substrates by kallikrein-related proteinases is described.