Glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides: Revised kinetic mechanism and kinetics of ATP inhibition

Kinetic mechanism and some properties of glucose-6-phosphate dehydrogenase from sheep brain cortex

“…In reality, EAB (E.G6P.NADP + ) and EPQ (E.6PGA.NADPH) complexes likely exist transiently at very low concentrations that are kinetically not significant [35]. Furthermore it was formerly observed that, the dimeric G6PD follows either a Random or a Theorell-chance mechanism [34]. The observed kinetic behavior of G6PD from sheep brain cortex is in accordance with the enzyme from other sources [27,33].…”

“…Levy and his colleague established in their study that kinetic behavior of Leuconostoc mesenteroides changes according to the kind of its coenzyme. They defined that enzyme catalyze the reaction with random mechanism with NAD + but an ordered, sequential mechanism in the company of NADP + linked reaction [34]. Sheep brain cortex G6PD obeys 'Theorell-chance' mechanism.…”

Titration Calorimetry as a Tool to Determine Thermodynamic and Kinetic Parameters of Enzymes

“…This enzyme catalyzes the oxidation of glucose-6-phosphate (G6P) and presents an unusual dual-coenzyme specificity that plays an important role in the metabolism of the bacteria. 30 The G6PD from Leuconostoc mesenteroides is inhibited by ATP. 30 The thermogram in Figure 9.4(a) was obtained using a reaction medium with high concentrations of both glucose-6-phosphate and NAD + .…”

“…30 The G6PD from Leuconostoc mesenteroides is inhibited by ATP. 30 The thermogram in Figure 9.4(a) was obtained using a reaction medium with high concentrations of both glucose-6-phosphate and NAD + . Two injections of enzyme at very low concentration were made and the reaction could be followed in the steady state.…”

“…Figure 9.6 also shows the rates of reaction obtained in the presence of ATP, which acts as a competitive inhibitor of the G6PD. 29 The K m -value for NAD + 30 ITC also allows an accurate determination of thermodynamic parameters of activation since the actual temperature of the catalysed reaction is known. The temperature dependence of the reaction rate can be described by both the Arrhenius and the Eyring equations.…”