Effect of the C-terminal domain of Vibrio proteolyticus chitinase A on the chitinolytic activity in association with pH changes.

ABSTRACT

AIMS: To reveal the cause of the difference in activity of chitinase A from Vibrio proteolyticus and chitinase A from a strain of Vibrio carchariae (a junior synonym of Vibrio harveyi), we investigated the pH-dependent activity of full-length V. proteolyticus chitinase A and a truncated recombinant corresponding to the V. harveyi form of chitinase A. METHODS AND RESULTS: After overexpression in Escherichia coli strain DH5α, the full-length and truncated recombinant chitinases were purified by ammonium sulphate precipitation and anion exchange column chromatography. Chitinase activity was measured at various pH values using α-crystal and colloidal chitins as the substrate. The pH-dependent patterns of the relative specific activities for α-crystal chitin differed between the full-length and truncated recombinant chitinases, whereas those for colloidal chitin were similar to each other. CONCLUSION: The difference in the activity of V. proteolyticus chitinase A and V. harveyi chitinase A might be partly due to a change in the pH dependence of the chitinase activities against α-crystal chitin, resulting from C-terminal processing. SIGNIFICANCE AND IMPACT OF STUDY The present results are important findings for not only ecological studies on the genus Vibrio in association with survival strategies, but also phylogenetic studies.