Cloning, Expression, Purification, and Characterization of a Novel β-Galactosidase/α-L-Arabinopyranosidase from Paenibacillus polymyxa KF-1

Glycosidases are essential for the industrial production of functional oligosaccharides and many biotech applications. A novel β-galactosidase/α-L-arabinopyranosidase (PpBGal42A) of the glycoside hydrolase family 42 (GH42) from Paenibacillus polymyxa KF-1 was identified and functionally characterized. Using pNPG as a substrate, the recombinant PpBGal42A (77.16 kD) was shown to have an optimal temperature and pH of 30 °C and 6.0. Using pNPαArap as a substrate, the optimal temperature and pH were 40 °C and 7.0. PpBGal42A has good temperature and pH stability. Furthermore, Na+, K+, Li+, and Ca2+ (5 mmol/L) enhanced the enzymatic activity, whereas Mn2+, Cu2+, Zn2+, and Hg2+ significantly reduced the enzymatic activity. PpBGal42A hydrolyzed pNP-β-D-galactoside and pNP-α-L-arabinopyranoside. PpBGal42A liberated galactose from β-1,3/4/6-galactobiose and galactan. PpBGal42A hydrolyzed arabinopyranose at C20 of ginsenoside Rb2, but could not cleave arabinofuranose at C20 of ginsenoside Rc. Meanwhile, the molecular docking results revealed that PpBGal42A efficiently recognized and catalyzed lactose. PpBGal42A hydrolyzes lactose to galactose and glucose. PpBGal42A exhibits significant degradative activity towards citrus pectin when combined with pectinase. Our findings suggest that PpBGal42A is a novel bifunctional enzyme that is active as a β-galactosidase and α-L-arabinopyranosidase. This study expands on the diversity of bifunctional enzymes and provides a potentially effective tool for the food industry.