Biochemical and catalytic properties of two β-glycosidases purified from workers of the termite Macrotermes subhyalinus (Isoptera: Termitidae)

Abstract

Two s-glycosidases were purified from the termite Macrotermes subhyalinus (Rambur) workers by chromatography on gel filtration, ion exchange and hydrophobic interaction columns. The preparations were shown to be homogeneous on Polyacrylamide gel. Both enzymes have a similar molecular mass (68 KDa) and optimum pH (5.4) but differ in optimal temperature and thermal stability. The s-glycosidases preferred s-fucosides to s-glucosides, s-galactosides and s-xylosides, and hydrolysed glucose-glucose-s-(l-4) linkages better than s-(l-3), s-(l-2) and s-(l-6) linkages. They did not hydrolyse saccharides such as melibiose, sucrose, lactose, xylobiose, melizitose, stachyose, lactose, raffinose, laminarin, arabinogalactan, carboxymethylcellulose, inulin, lichenan and starch. s-Glycosidase A and s-glycosidase B of M. subhyalinus workers are capable of catalysing transglucosylation reactions. The yields of glucosylation of hydroxyamino acid derivatives and phenylethanol, catalysed by the two enzymes in the presence of cellobiose as glucosyl donor, were lower than those reported previously with conventional sources of s-glycosidases. In addition, the optimum pH is different for the hydrolysis and trans glucosylation reactions.On the basis of this work, it is proposed that the physiological role of s-glycosidase A and s-glycosidase B of M. subhyalinus workers is the digestion of di- and oligosaccharides derived from hemicelluloses and celluloses.