Expression,purification, and characterization of human intestinal maltase secreted from Pichia pastoris

A gene encoding human intestinal maltase (HMA) was successfully expressed in Pichia pastoris under the control of the methanol-induced alcohol oxidase (AOX1) promoter. The secreted recombinant HMA fused with a His₆-tag was produced (150 U/L) and was easily purified from culture supernatants in a 3-step diafiltration, ultrafiltration, and affinity column chromatography protocol. The specific activity of the purified HMA was 16.8 U/mg. Endoglycosidase H digestion of the protein showed that the recombinant HMA was N-glycosylated. The purified HMA was maximally active at pH 6.5 and stable (≥90%) up to 65°C. The kinetic parameters K _m and V _max were 3.3±0.25 mM maltose and 61.9±2 U/mg, respectively.