Enzymatic Properties of Recombinant Rehmannia Class III Chitinase Expressed in Bacillus subtilis

Abstract

To investigate the enzymatic properties of an acidic class III chitinase of which gene, JHIII, was isolated from Rehmannia glutinosa, the recombinant protein, rJHII, was obtained from the culture of B. subtilis WB600 transformed with JHIII gene. It showed a maximum chitinolytic activity at pH 6 and 50oC, and revealed a relatively high enzymatic activity of more than 50% in the broad range of pH (pH 2 to pH 8) and temperature (20oC to 70oC). The catalytic activity of rJHI was lowered to 85% and 42% in the presence of 5M and 10 M allosamidin, respectively, which is a potent competitive inhibitor of family 18 chitinases. The rJHIII was considered as an endo-type enzyme because it hydrolyzed (GlcNAc)6 into (GlcNAc)₂, (GlcNAc)₃, and (GlcNAc)₄, but did not hydrolyze (GlcNAc)₂-5. The rJHI inhibited the growth of Fusarium oxysporum R2, which was isolated from the root of Rehmannia and identified as a specific fungal pathogen of Rehmannia. The inhibition by rJHIII was a dose-dependent manner.