[Cloning of Oryza sativa N-glycanase gene (OsPNGase A) and its expression in Pichia pastoris].

N-glycanase is a class of deglycosylation enzymes, widely used in the study of N-glycosylation modification of glycoprotein. In this study, an N-glycanase gene (OsPNGase A, XM_015775832) with high GC content (69.48%) was cloned from rice and then the yeast secretory expression vector pPICZ(α)A-OsPNGase A was constructed for the purpose of transformation to Pichia pastoris. After induction in Pichia pastoris SMD1168H, the target protein was purified by DEAE Sepharose and HisTrap HP chromatography, with a yield of 12.3 mg OsPNGase A from 1 L fermentation medium, showing a specific activity of 258 U/mg. SDS-PAGE revealed that the purified OsPNGase A was a single band and showed consistentcy with the expected molecular weight. OsPNGase A could act on transferrin recombinantly expressed in rice, avidin recombinantly expressed in corn and horseradish peroxidase. Furthermore, OsPNGase A showed higher activity than commercial PNGase F towards avidin. OsPNGase A displayed the highest digestion activity at pH 6.0 and 40 °C, and was also active in the neutral and alkaline environment. Despite the fact that OsPNGase A was inhibited by reducing agents and surfactants, it still maintained partial enzymatic activity in 100 mmol/L β-ME or DTT. Therefore, the successful expression of rice OsPNGase A provides a new tool for the study of plant glycoproteins and the establishment of yeast secretion expression system lays the foundation for the preparation of PNGase A.