Electron transport system, hepatic

The mechanism in hepatic cellular metabolism involves an electron transport system that functions for many drugs and chemical substances. These reactions include O-demethylation, N-demethyla-tion, hydroxylation, nitro reduction and other classical biotransformations. The electron transport system contains the heme protein, cytochrome P-450 that is reduced by NADPH via a flavoprotein, cytochrome P-450 reductase. For oxidative metabolic reactions, cytochrome P-450, in its reduced state (Fe 2), incorporates one atom of oxygen into the drug substrate and another into water. Many metabolic reductive reactions also utilize this system. In addition, there is a lipid component, phosphatidylcholine, which is associated with the electron transport and is an obligatory requirement for... 

Hepatic mitochondria isolated from copper-deficient animals were found to be deficient in the cytochrome oxidase activity which correlated well with hem synthesis (57). Failure to synthesize hem from ferric iron and protoporphyrin could be enhanced by succinate or inhibited by cyanide, which suggests that the reduction from ferric to ferrous requires an intact electron transport system in order for hem synthesis to go into completion. 

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