INHIBITION OF RAT-TISSUE KALLIKREIN GENE FAMILY MEMBERS BY RAT KALLIKREIN-BINDING PROTEIN AND ALPHA-1-PROTEINASE INHIBITOR

The regulation of tissue kallikrein activity by plasma serine proteinase inhibitors (serpins) was investigated by measuring the association rate constants of six tissue-kallikrein family members isolated from the rat submandibular gland, with rat kallikrein-binding protein (rKBP) and alpha-1-proteinase inhibitor (alpha-1-PI). Both these serpins inhibited kallikreins rK2, rK7, rK8, rK9 and rK10(1) with association rate constants in the 10(3)-10(4) M-1.s-1 range, whereas only 'true' tissue kallikrein rK1 was not susceptible to alpha-1-PI. This results in slow inhibition of rK1 by plasma serpins, which could explain why this kallikrein is the ony member of the gene family identified so far that induces a transient decrease in blood pressure when injected in minute amounts into the circulation.