Cytochrome c reductase and

Antimycin A-insensitive NADH cytochrome c reductase and cytochrome c oxidase Absorbance plots of OD550 for 1 min need to follow... 

Pretreatment with the Type I substrate, ethylmorphine, resulted in 100% mortality in both rats and mice, and aminopyrine pretreatment resulted in 100% and 64% mortality in rats and mice, respectively, exposed to disulfoton (Pawar and Fawade 1978). Nickel chloride, cobalt chloride, or cycloheximide decreased the levels of cytochrome bs, cytochrome c reductase, and total heme in rats (Fawade and Pawar 1983). These electron transport components were further decreased in rats pretreated with these inhibitors and given a single dose of disulfoton. Data from this study suggests an additive effect, since disulfoton also decreases the activities of these components. Evidence of an additive effect between disulfoton and these metabolic inhibitors was suggested by the decrease in ethylmorphine N-demethylase and acetanilide hydroxylase activities when rats were given an inhibitor followed by disulfoton. In another experiment, these inhibitors decreased the activity of delta-aminolevulinic acid synthetase, but this decrease was reversed when disulfoton was administered. 

Seasonal Study of Mixed Function Oxidases.— A seasonal study of hepatic microsomal mfo components has been conducted in female R and S fish (submitted for publication). Components studied were cytochromes P-450 and 5, NADPH-cytochrome c reductase, NADPH-dichlorophenolindophenol reductase, NADH-cytochrome c reductase and NADH-cytochrome 5 reductase. All were monitored at 30°C by standard spectrophotometric methods following optimization procedures (8, 9 > 10, n, J 2). Microsomal and total hepatic protein (137 and liver weight to body weight ratios were also monitored. 

This enzyme [EC 1.6.2.4] (also referred to as NADPH ferrihemoprotein reductase, NADPHxyto-chrome P450 reductase, TPNH2 cytochrome c reductase, and ferrihemoprotein P450 reductase) catalyzes the reaction of NADPH with two ferricytochrome to produce NADP+ and two ferrocytochrome. The protein requires FMN and FAD. In addition, it also catalyzes the reduction of heme-thiolate-dependent monooxygenases (e.g.,... 

Liver microsomal enzyme inducers that are lipid soluble at the physiologic pH can be classified into two general groups. Some, such as phenobarbital, tend to stimulate all enzymes others, such as 3-methylcholanthrene, tend to be selective. The administration of phenobarbital increases the amounts of NADPH-cytochrome C reductase and P-450, and the rate of P-450 reduction. In contrast, the administration of 3-methylcholanthrene increases the amount of P-450 but neither the activity of NADPH-cytochrome C reductase nor the rate of P-450 reduction. 

Elemental sulfur was also formed during sulfide oxidation by a cytochrome c-flavocytochrome c-552 complex in Chromatium vinosum (42). Flavocytochromes of different phototrophic bacteria act as sulfide cytochrome c reductases and there was one report that a flavocytochrome possessed even elemental sulfur reductase activity (see 4.9V All flavocytochromes examined so far are heat-labile and are reduced by sulfide forming thiosulfate under strictly anaerobic conditions (4.9V The small acidic cytochromes c-551 of Ectothiorhodospira halochloris and Ectothiorhodospira abdelmalekii. both located on the outside of the cell membrane, stimulated the velocity of sulfide... 

Intestinal Caco-2 cells provide useful models for assessing the effect of xeno-biotics on enzyme activity. Thus, Faist et al.291 have studied the effect of melanoidins both on a Phase-I enzyme, NADPH cytochrome c reductase, and a Phase-II enzyme, glutathione S-transferase. Where the results achieved a significant level, activity was reduced, thus implying that detoxification would be less efficient in the presence of the melanoidins tested. However, some other results pointed the other way (see Chapter 6). 

T. Hofmann, H. F. Erbersdobler, I. Kruse, and V. Faist, Molecular weight distribution of non-enzymatic browning products in Japanese soy sauce and studies on their effects on NADPH-cytochrome c-reductase and glutathione-S-transferase in intestinal cells, in G, 2002, 485 186. 

It is important that samples used in this assay are free of cytochrome oxidase or cytochrome-c reductase and indeed of superoxide which also reduces cytochrome c. 

Weiss, H., and Kolb, H. J., 1979, Isolation of mitochondrial succinate ubiquinone reductase, cytochrome c reductase and cytochrome c oxidase from Neurospora crassa using nonionic detergent, Eur. J. Biochem. 99 139nl49. 

Weiss, H., and Leonard, K., 1987, Structure and function of mitochondrial ubiquinol cytochrome c reductase and NADH ubiquinone reductase, Chemica Scripta 27B 73n 81. 

Fig. 46. Comparison of the absorption spectra of wild-type and mutant (cys G-439 and cys 1-68) sulfite reductases from Salmonella typhimurium. Spectra of S. typhi-murium sulfite reductase, cys G-439 NADPH-cytochrome c reductase, and cys 1-68 NADPH-cytochrome c reductase, each dissolved in 0.05 M potassium phosphate buffer, pH 7.7, containing 0.1 mM EDTA, were read against a blank containing only buffer. The spectrum of each enzyme is presented in terms of its millimolar extinction coeflScients, assuming 8 moles of flavin per mole of enzyme. Light broken line, calculated difference spectrum between those of wild-type and cys G enzymes when both enzyme solutions contain equal concentrations of flavin. From Siegel et al. (.394).

Li L. Zheng LX. Yang FY. Effect of propensity of hexagonal II phase formation on the activity of mitochondrial ubiquinol-cytochrome c reductase and H(-i-)-ATPase. Chem Phys Lipids 1995 76 135-144. Litman B J, Lewis EN, Levin IW. Packing characteristics of highly unsatrrrated bUayer lipids Raman spec-... 

Figure 3. DeDuve plots of relative specific activities (specific activity/specific activity in PNS) in various fractions. Key to fractions PNS, postnuclear supernatant SOL, soluble MIT, mitochondria MIC, microsomes and Nl, N2, N3, and N4, the discontinuous gradient fractions (see Figure 2). Key to activities A, 5 -nucleotidase B, succinate-cytochrome c reductase and C, NADPH-cytochrome...

Miwa, G.T., S.B. West, and A.Y.H. Lu (1978). Studies on the rate-limiting enzyme component in the microsomal monooxygenase system. Incorporation of purified NADPH cytochrome c-reductase and cytochrome P450 into rat liver microsomes. JBC 253, 1921-1929. 

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