[Trypsin and microbial serine proteinase inhibitors isolated from Yersinia pseudotuberculosis]

A novel 9 kD protein inhibitor of trypsin and related proteinases was purified from culture filtrate of Yersinia pseudotuberculosis by ultrafiltration, affinity chromatography, and gel filtration. The protein is stable at pH from 1 to 9. The inhibitor activity dramatically decreases at temperature above 37 degrees C. The purified inhibitor significantly suppresses activities of an endogenous trypsin-related proteinase and trypsin but does not affect chymotrypsin, pepsin, and papain. One molecule of yersinia inhibitor binds two molecules of endogenous trypsin-related proteinase and about one trypsin molecule. The Ki for yersinia proteinase is 1.7.10(-7) and Ki for trypsin is 2.4.10(-7). Amino acid composition of the inhibitor is characterized by the presence of beta-aminobutyric acid and ornithine and relatively high contents of alanine and arginine whereas cysteine, histidine, and proline are absent.