Deoxynojirimycin enhanced the transglycosylation activity of a glycosidase from the China white jade snail.

A beta-D-glycosidase (G I) from the China white jade snail showed non-Michaelis-Menten mode in catalyzing the reaction using pNPGlu and pNPFuc as the substrate and monitoring the released pNP. We determined quantitatively both the transglycosidic and hydrolytic products of pNPGlu and pNPFuc solvolysis for the detailed kinetic analysis on G I-catalyzed hydrolysis and transglycosylation reaction. The inhibition kinetic studies using deoxynojirimycin (DNJ) and butanol as inhibitors were preceded. DNJ only inhibited competitively the hydrolysis of cellobiose and pNPGlu while "activated" the transglycosylation of pNPGlu and pNPFuc. This was evident from the increased V(max)tr value with no change of the apparent K(m)tr. In contrast, butanol exhibited a competitive inhibition to the transglycosylation reaction and non-competitive inhibition to the hydrolysis. The results indicated that the non-Michaelis-Menten kinetic behavior was caused by the co-occurrence of substrate transglycosylation reaction. This study provided a simple method to increase the transglycosylation yield by using DNJ to inhibit hydrolysis.