Enzyme kinetics of ginsenosidase type IV hydrolyzing 6-O-multi-glycosides of protopanaxatriol type ginsenosides

In this work, the kinetics of ginsenosidase type IV hydrolyzing the 6-O-multi-glycosides of protopanaxatriol type ginsenosides (PPT) from Aspergillus sp.39g strain were investigated. The enzyme molecular weight was about 56 kDa. The enzyme hydrolyzes the 6-O-alpha-L-(1 -> 2)-rhamnoside of ginsenoside Re and 6-O-beta-D-(1 -> 2)-xyloside of R1 into Rg1, and subsequently hydrolyzes 6-O-beta-D-glucoside of Rg1 into F1. The enzyme hydrolyzes 6-O-alpha-L-(1 -> 2)-rhamnoside of Rg2 and 6-O-beta-D-(1 -> 2)-glucoside of Rf into Rh1, and subsequently hydrolyzes 6-O-beta-D-glucoside of Rh1 into its aglycone. The enzyme K-m and V-max for Re were 22.2 mM, and 7.94 mM/h; the K-m and V-max for R1 were 7.06 mM and 1.61 mM/h; the enzyme transformation velocity (V-0) at 5 mM substrate was 1.46 mM/h for Re, and 0.67 mM/h for R1. Therefore, the enzyme hydrolysis on the Re rhamnoside was faster than that on R1 xyloside. The enzyme V-0 on Rg1 was 0.05 mM/h that indicated the enzyme hardly hydrolyzed the 6-O-beta-D-glucoside of Rg1. The enzyme kinetic parameters of Rg2 and Rf were 5.74 and 9.43 mM for K-m: 2.70 and 2.84 mM/h for V-max: 1.26 and 0.98 mM/h for V-0 at 5 mM substrate, respectively. Thus the enzyme hydrolysis on Rg2 rhamnoside was faster than that on the glucoside of Rf. (C) 2011 Elsevier Ltd. All rights reserved.