Inhibitory Effects of Pentagalloylgulcose on Reduced Nicotinamide Adenine Dinucleotide Dehydrogenase of Photobacterium phosphoreum

Abstract

Inhibitory effects of pure pentagalloylglucose (1, 2, 3, 4, 6-penta-O-galloyl-β-D-glucose) on purified nicotinamide adenine dinucleotide (NADH) dehydrogenase of the respiratory chain of Photobacterium phosphoreum were investigated. Pentagalloylglucose inhibited the NADH-ubiquinone-1, NADH-menadione, and NADH-2, 6-dichlorophenolindophenol oxidoreductase activities with less than 150nM of a 50% inhibition concentration (IC₅₀), but hardly inhibited NADH-ferricyanide and NADH-cytochrome c oxidoreductase activities with at least less than 0.5μM of pentagalloylglucose.Pentagalloylglucose inhibited noncompetitively the NADH dehydrogenase pf P. phosphoreum, which belongs to NADH dehydrogenase II (NADH dh II), and its inhibitor constant (K_i) to NADH-ubiquinone-1 oxidoreductase activity was estimated as 30nM of pentagalloylglucose. Therefore, pentagalloylglucose is the potent inhibitor of NADH dh II, more than flavone (IC₅₀=150μM for NADH-ubiquinone-1 oxidoreductase activity) which has previously been reported as an inhibitor for NADH dh II.