Kinetic mechanism of glucose dehydrogenase from Halobacterium salinarum

The kinetic mechanism of glucose dehydrogenase (EC 1.1.1.47) from Halobacte rium salinarum was studied by initial velocity and product inhibition metho ds. The results suggest that both, in the forward and reverse direction, th e reaction mechanism is of Bi Bi sequential ordered type involving formatio n of ternary complexes. NADP(+) adds first and NADPH formed dissociates fro m the enzyme last. For the reverse direction, NADPH adds first and NADP(+) leaves last. Product inhibition experiments indicate that (a), the coenzyme s compete for the same site and form of the enzyme and (b), ternary abortiv e complexes of enzyme-NADP(+)-glucono-delta-lactone and enzyme-NADPH-glucos e are formed. All the other inhibitions are noncompetitive.