Glyceraldehyde - 3 - Phosphate Dehydrogenase - catalyzed Chain Oxidation of Reduced Nicotinamide Adenine Dinucleotide

The chain oxidation of glyceraldehyde-3-phosphate dehydrogenase *NADH by perhydroxyl radicals and propagated by molecular oxygen was studied by the xanthine-xanthine oxidase system, ‘OCo y-ray, and pulse radiolysis. The chain length, amount of NADH oxidized per HOz generated, increases with increasing acidity of the medium and reaches a value of 73 at pH 5.0. The rate constant for the oxidation of the glyceraldehyde-3-phosphate dehydrogenase NADH complex by HOz was estimated to be 2 X lo’ M-’ s-’ at ambient temperatures (23-24°C). Rate studies as a function of pH indicate that 02is unreactive toward the glyceraldehyde-3-phosphate dehydrogenaseaNADH complex. Other dehydrogenases (malate dehydrogenase, glutamate dehydrogenase, and isocitric dehydrogenase) studied showed no catalytic activity in the oxidation of NADH by HOz/Oz-.