Biochemical Characterization of a Catalase from Vibrio vulnificus, a Pathogen Causing Gastroenteritis

Abstract

Vibrio vulnificus is an extremely virulent human pathogen causing gastroenteritis and possibly life threatening septicemia in patients and most of V. vulnificus are catalase positive that can deactivate the peroxide radicals, thus allowing them to survive within the host. In the current research, a catalase from V. vulnificus (CAT-Vv) was purified to homogeneity after expression in Escherichia coli. The catalytic kinetics and function of CAT-Vv were further examined. CAT-Vv catalyzed the reduction of H₂O₂ with an optimal pH of 7.5 and a temperature optimum of 37°C. The V_max and K_m values were 65.8±1.2 U/mg and 10.5±0.7 mM for H₂O₂. The mutation analysis suggests the amino acids involved in heme binding play a key role in the catalysis. Quantitative reverse transcription-PCR revealed that transcription of CAT-Vv was up-regulated by low salinity, heat, and oxidative stresses. The research will give new clues to inhibit the growth and infection of V. vulnificus.