Nicotinamide oxidase

Ohkubo, M., and Fujimura, S. Rat liver N-methyl-nicotinamide oxidase I and II Substrate non-specific enzyme "aldehyde oxidase" and specific enzyme. Biochem Int 4 353-358, 1982. 

More recently, flavin-dependent nicotinamide oxidases, such as YcnD from Bacillus subtilis [754] or an enzyme from Lactobacillus sanfranciscensis [755] were employed for the oxidation of nicotinamide cofactors at the expense of molecular oxygen producing H2O2 or (more advantageous) H2O via a two- or four-electron transfer reaction, respectively [756-758]. Hydrogen peroxide can be destroyed by addition of catalase and in general, both NADH and NADPH are accepted about equally well. 

Cu-+ Peroxidase Cytochrome oxidase Nicotinamide adenine dinucleotide (NAD) Hydride ion (H ) Alcohol dehydrogenase... 

Inflammatory cell phenomenon are also contributors to lipid peroxidation. Activated neutrophils may adhere to damaged endothelium and amplify traumatic, ischaemic or ischaemia-reperfiision injury. Many cyclooxygenase products of the metabolism of atachidonic acid modulate the inflammatory responses of cells. Macrophages, neutrophils and microglia are important sources of reactive oxygen at the injury site. When activated, they produce a respiratory burst that is traced to activated nicotinamide adenine dinucleotide (NADPH/NADH) oxidase. 

Figure 18.2 Summary of respiratory energy flows. Foods ate converted into the reduced form of nicotinamide adenine dinucleotide (NADH), a strong reductant, which is the most reducing of the respiratory electron carriers (donors). Respiration can he based on a variety of terminal oxidants, such as O2, nitrate, or fumarate. Of those, O2 is the strongest, so that aerobic respiration extracts the largest amount of free energy from a given amount of food. In aerobic respiration, NADH is not oxidized directly by O2 rather, the reaction proceeds through intermediate electron carriers, such as the quinone/quinol couple and cytochrome c. The most efficient respiratory pathway is based on oxidation of ferrocytochrome c (Fe ) with O2 catalyzed by cytochrome c oxidase (CcO). Of the 550 mV difference between the standard potentials of c)Tochrome c and O2, CcO converts 450 mV into proton-motive force (see the text for further details).

P. Mitchell (Nobel Prize for Chemistry, 1978) explained these facts by his chemiosmotic theory. This theory is based on the ordering of successive oxidation processes into reaction sequences called loops. Each loop consists of two basic processes, one of which is oriented in the direction away from the matrix surface of the internal membrane into the intracristal space and connected with the transfer of electrons together with protons. The second process is oriented in the opposite direction and is connected with the transfer of electrons alone. Figure 6.27 depicts the first Mitchell loop, whose first step involves reduction of NAD+ (the oxidized form of nicotinamide adenosine dinucleotide) by the carbonaceous substrate, SH2. In this process, two electrons and two protons are transferred from the matrix space. The protons are accumulated in the intracristal space, while electrons are transferred in the opposite direction by the reduction of the oxidized form of the Fe-S protein. This reduces a further component of the electron transport chain on the matrix side of the membrane and the process is repeated. The final process is the reduction of molecular oxygen with the reduced form of cytochrome oxidase. It would appear that this reaction sequence includes not only loops but also a proton pump, i.e. an enzymatic system that can employ the energy of the redox step in the electron transfer chain for translocation of protons from the matrix space into the intracristal space. 

Nicotinamide Adenine Dinucleotide (NAD+) Alcohol dehydrogenase, Lactate oxidase... 

The answers are 34-g, 35-a, 36-d. (Katzung, pp 53—56J There are four major components to the mixed-function oxidase system (1) cytochrome P450, (2) NAD PH, or reduced nicotinamide adenine dinucleotide phosphate, (3) NAD PH—cytochrome P450 reductase, and (4) molecular oxygen. The figure that follows shows the catalytic cycle for the reactions dependent upon cytochrome P450. 

A number of autoxidation reactions exhibit exotic kinetic phenomena under specific experimental conditions. One of the most widely studied systems is the peroxidase-oxidase (PO) oscillator which is the only enzyme reaction showing oscillation in vitro in homogeneous stirred solution. The net reaction is the oxidation of nicotinamide adenine dinucleotide (NADH), a biologically vital coenzyme, by dioxygen in a horseradish peroxidase enzyme (HRP) catalyzed process ... 

Hexachloroethane is metabolized by the mixed function oxidase system by way of a two-step reduction reaction involving cytochrome P-450 and either reduced nicotinamide adenine dinucleotide phosphate (NADPH) or cytochrome b5 as an electron donor. The first step of the reduction reaction results in the formation of the pentachloroethyl free radical. In the second step, tetrachloroethene is formed as the primary metabolite. Two chloride ions are released. Pentachloroethane is a minor metabolic product that is generated from the pentachloroethyl free radical. 

Curnutte, J. T. (1985). Activation of human neutrophil nicotinamide adenine dinucleotide phosphate, reduced (triphosphopyridine nucleotide, reduced) oxidase by arachidonic acid in a cell-free system. J. Clin. Invest. 75, 1740-3. 

Cassatella, M. A., Hartman, L., Perussia, B., Trinchieri, G. (1989). Tumor necrosis factor and immune interferon synergistically induce cytochrome b.245 heavy-chain gene expression and nicotinamide-adenine dinucleotide phosphate hydrogenase oxidase in human leukemic myeloid cells. J. Clin. Invest. 83,1570-9. 

Cumutte, J. T., Berkow, R. L., Roberts, R. L., Shurin, S. B., Scott, P. J. (1988). Chronic granulomatous disease due to a defect in the cytosolic factor required for nicotinamide adenine dinucleotide phosphate oxidase activation. J. Clin. Invest. 81,606-10. 

N-dealkylation results from an alkyl substitution on an aromatic molecule, which is one of the first places where microorganisms initiate catabolic transformation of atrazine, a xenobiotic molecule (Fig. 15.2). It is a typical example of a reaction leading to transformation of pesticides like phenyl ureas, acylanihdes, carbamates, s-tri-azines, and dinitranilines. The enzyme mediating the reaction is a mixed-function oxidase, requiring a reduced nicotinamide nucleotide as an H donor. 

Boron also appears to be involved in redox metabolism in cell membranes. Boron deficiency was shown to inhibit membrane H -ATPase isolated from plant roots, and H -ATPase-associated proton secretion is decreased in boron-deficient cell cultures [71]. Other studies show an effect of boron on membrane electron transport reactions and the stimulation of plasma reduced nicotinamide adenine dinucleotide (NADH) oxidase upon addition of boron to cell cultures [72, 73]. NADH oxidase in plasma membrane is believed to play a role in the reduction of ascorbate free radical to ascorbate [74]. One theory proposes that, by stimulating NADH oxidase to keep ascorbate reduced at the cell wall-membrane interface, the presence of boron is important in... 

Cholesterol is transported into the mitochondria of steroidogenic tissue, where side chain cleavage is carried out. In common with other mixed-function oxidase systems, the cholesterol side chain cleavage requires reduced nicotinamide-adenine dinucleotide phosphate... 

Enzymes responsible for metabolism are located at various subcellular sites, for example the cytosol, mitochondria and smooth endoplasmic reticulum. However, it is enzymes derived from endoplasmic reticulum, called mixed function oxidases or monooxygenases , which have been most intensely studied in the past two or three decades. These enzyme systems, which utilize a family of haemoprotein cytochromes, or P-450 as terminal oxidases, require molecular oxygen and reduced nicotinamide adenine dinucleotide phosphate (NADPH) for activity. The overall stoichiometry of the reactions catalyzed by these enzymes is normally represented by equation (1). 

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