Abstract: A wild-type proteinase K expression strain was obtained. Then three amino acid residue positions that had potential effects on its thermal stability were obtained through software prediction, and point mutations were performed on them in Pichia pastoris GS115, respectively. Secreted expression was carried out, a proteinase K mutant pPicZαA-PK108 with a 30% increase in thermal stability and an approximately 50% increase in specific activity was obtained. This study had played a certain role in promoting the application of proteinase K in industry. It can reduce the amount of proteinase K used in detergent and food industry, and reduce production costs. In addition, it can also improve the efficiency of virus inactivation in sewage and reduce the environment pollution.

Key words: proteinase K, Pichia pastoris, mutation, thermal stability