In this paper, the kinetics of a cloned special glucosidase,
named ginsenosidase type III hydrolyzing 3-O-glucoside
of multi-protopanaxadiol (PPD)-type ginsenosides, were
investigated. The gene (bgpA) encoding this enzyme was
cloned from a Terrabacter ginsenosidimutans strain and
then expressed in E. coli cells. Ginsenosidase type III
was able to hydrolyze 3-O-glucoside of multi-PPD-type
ginsenosides. For instance, it was able to hydrolyze the 3-
O-β-D-(1→2)-glucopyranosyl of Rb1 to gypenoside XVII,
and then to further hydrolyze the 3-O-β-D-glucopyranosyl
of gypenoside XVII to gypenoside LXXV. Similarly, the
enzyme could hydrolyze the glucopyranosyls linked to the
3-O- position of Rb2, Rc, Rd, Rb3, and Rg3. With a larger
enzyme reaction Km value, there was a slower enzyme
reaction speed; and the larger the enzyme reaction Vmax
value, the faster the enzyme reaction speed was. The Km
values from small to large were 3.85 mM for Rc, 4.08 mM
for Rb1, 8.85 mM for Rb3, 9.09 mM for Rb2, 9.70 mM for
Rg3(S), 11.4 mM for Rd and 12.9 mM for F2; and Vmax
value from large to small was 23.2 mM/h for Rc, 16.6 mM/h
for Rb1, 14.6 mM/h for Rb3, 14.3 mM/h for Rb2, 1.81mM/h
for Rg3(S), 1.40 mM/h for Rd, and 0.41 mM/h for F2.
According to the Vmax and Km values of the ginsenosidase
type III, the hydrolysis speed of these substrates by the
enzyme was Rc>Rb1>Rb3>Rb2>Rg3(S)>Rd>F2 in order.