Methyl parathion hydrolase can biodegrade organophosphorus pesticides. Due to its special application value,researchers paid more and more attension. Wild-type MPH-Och from Ochrobactrum sp. could not be secreted in Pichia pastoris. In order to increase the secretion level,the MPH-S274 Q mutant,which thermal stability was increased,was expressed in Pichia pastoris. After recombinant strain was induced by shaking culture flask for 120 h,the enzyme activity of culture supernatant reached 0. 7 U/m L. It was 14 ...