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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.
The NADPH system is also responsible for generating free radicals in immune cells by NADPH oxidase. These radicals are used to destroy pathogens in a process termed the respiratory burst . [ 13 ] It is the source of reducing equivalents for cytochrome P450 hydroxylation of aromatic compounds , steroids , alcohols , and drugs .
Unlike mammals, yeast (Saccharomyces cerevisiae) do not have several isoforms of FMO, but instead only have one called yFMO. This enzyme does not accept xenobiotic compounds. Instead, yFMO helps to fold proteins that contain disulfide bonds by catalyzing O 2 and NADPH-dependent oxidations of biological thiols, just like mammalian FMO's.
These enzymes do not transport protons, and, therefore, reduce ubiquinone without altering the electrochemical gradient across the inner membrane. [44] Another example of a divergent electron transport chain is the alternative oxidase, which is found in plants, as well as some fungi, protists, and possibly some animals.
The structure of this enzyme is highly conserved to maintain precisely the alignment of electron donor NADPH and acceptor FAD for efficient electron transfer. [26] The two electrons in reduced FAD are transferred one a time to adrenodoxin which in turn donates the single electron to the heme group of the mitochondrial P450.
The glyoxylate reductase enzyme localizes to the cell cytoplasm in plants. It can use both NADPH and NADH as a cofactor, but prefers NADPH. The enzyme substrate, glyoxylate, is a metabolite in plant photorespiration, and is produced in the peroxisome. Glyoxylate is important in the plant cell as it can deactivate RUBISCO and inhibit its activation.
Its structure was determined and reported in 1935 and given the name riboflavin, derived from the ribityl side chain and yellow colour of the conjugated ring system. [ 6 ] The first evidence for the requirement of flavin as an enzyme cofactor came in 1935.
This enzyme belongs to the family of oxidoreductases, specifically those acting on NADH or NADPH with NAD+ or NADP+ as acceptor. The systematic name of this enzyme is NADPH:NAD+ oxidoreductase (Si-specific). Other names in common use include non-energy-linked transhydrogenase, NAD(P)+ transhydrogenase (B-specific), and soluble transhydrogenase.