Abstract: Hydrogen peroxidase, commonly named catalase, has been widely used in food, textile and paper industries. A catalase gene cat1 was cloned from Enterobacter cloacae by using touch-down PCR and TAIL-PCR. Length of cat1 is 2 250 bp, which encode 749 amino acids and a termination codon. This gene was cloned into an expression vector pPIC9, and overexpressed in Pichia pastoris GS115 with the maximum catalase activity of 300 U/mL at shaker level. The recombinant CAT1 exhibited optimal activity at pH 6.5 and 37℃. Specific activity of CAT1 was 1667 U/mg, towards hydrogen peroxide as substrate. CAT1 remains above 80% enzyme activity after treated at 50 C for 2 h or stay at pH 5~8 for 1 h. The effects of CAT1 on glucose oxidase (GOD) activity was investigated. When the activity ratio of CAT1 to GOD was 1∶30, the GOD activity was no longer inhibited by hydrogen peroxide. This study also introduced a rapid screening method for P. pastoris with recombinant catalase.

Key words: catalase, Enterobacter cloacae, Pichia pastoris, gene expression, glucose oxidase