Properties of hepatic reduced nicotinamide adenine dinucleotide phosphate-cytochrome c reductase

Iyanagi, Takashi; Mason, Howard S.

doi:10.1021/bi00736a018

Cited by 357 publications

(178 citation statements)

References 37 publications

(31 reference statements)

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“…3). This observation was consistent with the formation of a ternary complex during the electron transfer from NADPH to cytochrome c mediated by the reductase and did not favor an ordered addition with NADPH as the first substrate ('binary' ping-pong mechanism [4]). …”

Section: Discussionsupporting

confidence: 79%

“…The number of (reactive) -SH groups per mol NADPH -cytochrome c reductase was estimated with Ellman's reagent (Nbs2) using a molar absorption coefficient of 14 140 M-l cm-' for 2-nitro-5-thiobenzoate anion [9] and a molecular weight of 68000 for the protease-solubilized NADPH -cytochrome c reductase [4]. The degree of -SH group modification was calculated from the amount of Nbs-liberated assuming 1 : 1 stoichiometry between Nbs-ions and mol thiol groups reacted.…”

Section: Determination Of -S H Content In Reductase Preparationsmentioning

confidence: 99%

“…A ratio A A455 / A A580 = 2.74 was determined for the pretreated reductase. This value indicated that more than 90% of the enzyme was transformed into the 0 2 -stable half-reduced state ( A A455/4 A585 = 2.73 -2.92 [4]). Nbs2 (final concentration 1 mM) was added to the half-reduced reductase and the absorbances at 412 nm and 580 nm monitored continuously for 5 h at + 4 "C.…”

Section: Reaction Of the 'Half-reduced' State Of Nadph-cytochrome C Rmentioning

confidence: 99%

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The Functional Role of Thiol Groups in Protease-Solubilized NADPH-Cytochrome c Reductase from Pork-Liver Microsomes

1977

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The total -SH content of protease-solubilized NADPH -cytochrome c reductase (EC 1.6.2.4) from pork liver microsomes was determined to be 5.9 k 0.3 mol thiol groups per mol of protein.Only three -SH groups of the protease-solubilized NADPH -cytochrome c reductase could be modified by 0.34 or 1.0 mM 5,5'-dithio-bis(2-nitrobenzoate) at pH 7.5 and + 4 "C. More than 95% of the original enzymatic activity was lost during this treatment. In the presence of 1 mM NADP+ only two -SH groups of the NADPH-cytochrome c reductase reacted with 5,5'-dithio-bis(2-nitrobenzoate). After removal of the competitive inhibitor NADP' , an enzyme derivative with the specific activity of the unmodified enzyme was obtained, containing two cysteinyl residues as mixed disulfides with 2-nitro-5-thiobenzoate. Renewed treatment of the modified reductase with 0.34 or 1 .O mM 5,5'-dithio-bis(2-nitrobenzoate) resulted in the modification of one additional thiol group under complete inactivation ( k for modification = 0.027 min-', k for inactivation = 0.039 min-' at 0.34 mM Nbsz, pH 7.5, + 4 "C). Kinetic analysis confirmed the suggestion that a single thiol group of the NADPH-cytochrome c reductase was protected by NADP+ against the reaction with 5,5'-dithio-bis(2-nitrobenzoate). Cytochrome c (58 pM) apparently enhanced the effect of NADP'. The modification of the accessible thiol groups by 1 mM 5,5'-dithio-bis(2-nitrobenzoate) did not affect the half-reduced state of the NADPH -cytochrome c reductase.

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Section: Discussionsupporting

confidence: 79%

Section: Determination Of -S H Content In Reductase Preparationsmentioning

confidence: 99%

Section: Reaction Of the 'Half-reduced' State Of Nadph-cytochrome C Rmentioning

confidence: 99%

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The Functional Role of Thiol Groups in Protease-Solubilized NADPH-Cytochrome c Reductase from Pork-Liver Microsomes

1977

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“…The flavoprotein, with either an FAD [2, 19, 21 -26, 291 or FMN prosthetic group [20], often has independent NADH:acceptor reductase activities [9, 19, 20, 22, 25, 27, 29 -311. Reducing equivalents are then transferred to a second redox centre, often an iron-sulphur centre [9,19,20,23,24,28,29,32,331 or an FMN [21].…”

Section: Discussionmentioning

confidence: 99%

Electron transfer reactions in the soluble methane monooxygenase of Methylococcus capsulatus (Bath)

Lund

Woodland

Dalton

1985

European Journal of Biochemistry

127

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1. Aerobic stopped-flow experiments have confirmed that component C is the methane monooxygenase component responsible for interaction with NADH. Reduction of component C by NADH is not the rate-limiting step for component C in the methane monooxygenase reaction.2. Removal and reconstitution of the redox centres of component C suggests a correlation between the presence of the FAD and Fe2S2 redox centres and NADH: acceptor reductase activity and methane monooxygenase activity respectively, consistent with the order of electron flow: NADH + FAD + Fe2S2 4 component A. This order suggests that component C functions as a 2e-'/le-' transformase, splitting electron pairs from NADH for transfer to component A via the one-electron-carrying Fe2S2 centre.3. Electron transfer has been demonstrated between the reductase component, component C and the oxygenase component, component A, of the methane monooxygenase complex from Methylococcus capsulatus (Bath) by three separate methods. This intermolecular electron transfer step is not rate-determining for the methane monooxygenase reaction.4. Intermolecular electron transfer was independent of component B, the third component of the methane monooxygenase. Component B is required to switch the oxidase activity of component A to methane monooxygenase activity, suggesting that the role of component B is to couple substrate oxidation to electron transfer, via the methane monooxygenase components.

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“…The difference is not completely explained in terms of molecular structure of the flavoproteins, but clear experimental evidence has been given to answer the question why microsomal flavoproteins catalyze one-electron reduction of quinones (119)(120)(121). Cytochrome P-450 reductase contains two flavins, FAD and FMN (119). The …”

Section: Ee-+ 2h+mentioning

confidence: 99%

Physiological Aspects of Free-Radical Reactions

Yamazaki¹,

Tamura²,

Nakajima³

et al. 1985

Environmental Health Perspectives

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Enzymes which catalyze the formation of free radicals in vitro will catalyze similar reactions in vivo. We believe that the formation of some kinds of free radicals has definite physiological meanings in metabolism. In this sense, the enzymes forming such free radicals are concluded to be in evolutionally advanced states. Elaborated structure and function of enzymes such as horseradish peroxidase and microsomal flavoproteins support the idea. Deleterious and side reactions caused by free radicals are assumed to be minimized in vivo by localizing the reactions, but this assumption should be verified by future studies.

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Properties of hepatic reduced nicotinamide adenine dinucleotide phosphate-cytochrome c reductase

Cited by 357 publications

References 37 publications

The Functional Role of Thiol Groups in Protease-Solubilized NADPH-Cytochrome c Reductase from Pork-Liver Microsomes

The Functional Role of Thiol Groups in Protease-Solubilized NADPH-Cytochrome c Reductase from Pork-Liver Microsomes

Electron transfer reactions in the soluble methane monooxygenase of Methylococcus capsulatus (Bath)

Physiological Aspects of Free-Radical Reactions

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