Inhibitory Effects of Tetragalloylglucose on the Complex II of Mitochondrial Respiratory Chain of Ascaris Muscle

The effect of tetragalloylglucose (1, 2, 3, 6-tetra-O-galloyl-β-D-glucose) on purified complex II (succinate-ubiquinone oxidoreductase) of the mitochondorial electron transport system of Ascaris muscle were studied. Both succinate-ubiquinone-1 (Q1) oxidoreductase, and succinate dehydrogenase measured with 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) in the presence of phenazine methosulfate (PMS) were inhibited by tetragalloylglucose. The inhibitions of both reductase activities of complex II were of competitive type, and the inhibitor constant (Ki) for Ascaris complex II (148nM) was lower than that for rat liver complex II (1.5μM). Thus, Ascaris complex II is much more sensitive to this inhibitor than the mammalian counterpart.