Rabbit brain glucose-6-phosphate dehydrogenase: biochemical properties and inactivation by free radicals and...

Glucose-6-phosphate dehydrogenase (G6PD) purified from rabbit brain is composed of two identical subunits of 56 kDa. The enzyme exhibits biphasic pH curve, linear Arrhenius plot and elevated susceptibility to inactivation by metal catalyzed oxidation and thiol binding reagents. 4-Hydroxy-2-nonenal (HNE) is able to inactivate the enzyme after only a few minutes of incubation. Since reactive oxygen species and G6PD-HNE adducts form easily in brain under conditions of oxidative stress, these findings have important implications in the loss of active G6PD molecules in vivo, a process which lowers the antioxidant protection and may be critical for neuron survival.