title: Subcellular distribution of OM cytochrome b-mediated NADH-semidehydroascorbate reductase activity in rat liver.
abstract: Tissue, cellular, and subcellular distributions of OM cytochrome b-mediated NADH-semidehydroascorbate (SDA) reductase activity were investigated in rat. NADH-SDA reductase activity was found in the post-nuclear particulate fractions of liver, kidney, adrenal gland, heart, brain, lung, and spleen of rat. Liver, kidney, and adrenal gland had higher NADH-SDA reductase activity than other tissues, and OM cytochrome b-dependent activity was 60-70% of the total activity. On the other hand, almost all of the reductase activity of heart and brain cells was mediated by OM cytochrome b. The ratio of the OM cytochrome b-mediated activities of NADH-SDA reductase to rotenone-insensitive NADH-cytochrome c reductase varied among these tissues. OM cytochrome b-mediated NADH-SDA reductase and rotenone-insensitive NADH-cytochrome c reductase activities were mainly present in the parenchymal cells of rat liver. The localization of the cytochrome-mediated reductase activities in the outer mitochondrial membrane was confirmed by subfractionation of liver mitochondria. Among the submicrosomal fractions, OM cytochrome b-mediated NADH-SDA reductase activity was highest in the cis-Golgi membrane fraction, in which monoamine oxidase activity was also highest. On the other hand, OM cytochrome b-mediated rotenone-insensitive NADH-cytochrome c reductase activity showed a slightly different distribution pattern from the NADH-SDA reductase activity. Thenoyltrifluoroacetone (TTFA), a metal chelator, effectively inhibited the NADH-SDA reductase activity, though other metal chelators did not affect the activity. TTFA failed to inhibit rotenone-insensitive NADH-cytochrome c reductase activity at the concentration which gave complete inhibition of NADH-SDA reductase activity.
mesh_terms: D000311:Adrenal Glands / Q000201:enzymology; D000818:Animals; D001921:Brain / Q000201:enzymology; D003573:Cytochrome b Group / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology; D008099:Liver / Q000201:enzymology*; D008862:Microsomes, Liver / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013347:Subcellular Fractions / Q000201:enzymology; D013367:Submitochondrial Particles / Q000201:enzymology
chemical_list: D003573:Cytochrome b Group; D009247:NADH, NADPH Oxidoreductases; C023927:monodehydroascorbate reductase (NADH)