Purification and characterization of an extracellular serine proteinase from Acanthamoeba castellanii

Abstract

An extracellular proteinase of A canthamoeba castellanii was purified and its biochemical and pathological properties were characterized, The molecular mass of the purified enzyme was similar to 42 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Sephacryl S-200 HR gel-filtration chromatography, Therefore, its structure seemed to be monomeric with a single polypeptide. Its activity was inhibited by the serine proteinase inhibitors diisopropyl fluorophosphate and phenylmethanesulfonyl fluoride. Its activity was optimum at 30 to 50 degreesC with a maximum at 50 degreesC; optimal pH was 8.0, As much as 70% of the enzyme activity was maintained at 50 degreesC for at least 12 h but was rapidly inactivated thereafter. The purified enzyme degraded collagen and rabbit corneal extract, Furthermore, it exhibited strong cytopathic effects on human corneal epithelial cells and fibroblast cells. These suggest the possible role of this enzyme in the pathogenesis of Acanthamoeba.