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NADPH oxidase (nicotinamide adenine dinucleotide phosphate oxidase) is a membrane-bound enzyme complex that faces the extracellular space. It can be found in the plasma membrane as well as in the membranes of phagosomes used by neutrophil white blood cells to engulf microorganisms.
For example, an enzyme that catalyzed this reaction would be an oxidoreductase: A – + B → A + B –. In this example, A is the reductant (electron donor) and B is the oxidant (electron acceptor).
Cytochrome P450 reductase (also known as NADPH:ferrihemoprotein oxidoreductase, NADPH:hemoprotein oxidoreductase, NADPH:P450 oxidoreductase, P450 reductase, POR, CPR, CYPOR) is a membrane-bound enzyme required for electron transfer from NADPH to cytochrome P450 [5] and other heme proteins including heme oxygenase in the endoplasmic reticulum [6] of the eukaryotic cell.
NADPH can also be generated through pathways unrelated to carbon metabolism. The ferredoxin reductase is such an example. Nicotinamide nucleotide transhydrogenase transfers the hydrogen between NAD(P)H and NAD(P) +, and is found in eukaryotic mitochondria and many bacteria. There are versions that depend on a proton gradient to work and ones ...
[109] [110] For example, the enzyme nicotinamidase, which converts nicotinamide to nicotinic acid, is a target for drug design, as this enzyme is absent in humans but present in yeast and bacteria. [43] In bacteriology, NAD, sometimes referred to factor V, is used as a supplement to culture media for some fastidious bacteria. [111]
They are phagocytic, and the respiratory burst is vital for the subsequent degradation of internalised bacteria or other pathogens. This is an important aspect of the innate immunity. Respiratory burst requires a 10 to 20 fold increase in oxygen consumption through NADPH oxidase (NOX2 in humans) activity.
An important example is EC 7.1.1.9 cytochrome c oxidase, the key enzyme that allows the body to employ oxygen in the generation of energy and the final component of the electron transfer chain. Other examples are: EC 1.1.3.4 Glucose oxidase; EC 1.4.3.4 Monoamine oxidase; EC 1.14.-.- Cytochrome P450 oxidase; EC 1.6.3.1 NADPH oxidase
[8] In this disorder, there is decreased activity of phagocyte NADPH oxidase; neutrophils are able to phagocytize bacteria but cannot kill them in the phagocytic vacuoles. The cause of the killing defect is an inability to increase the cell's respiration and consequent failure to deliver activated oxygen into the phagocytic vacuole. [5]