Cytochrome P450 heme-containing

In contrast to the above reductases which contain only a single flavin moiety, NADPH-cytochrome P450 reductase contains both FMN and FAD One flavin may be presumed to accept two reducing equivalents from NADPH while the other serves as a one-electron reductant for the heme iron of cytochrome 450- Flavin resolution and reconstitution studies have shown that the FAD moiety is the low-potential flavin that accepts reducing equivalents from NADPH while the FMN moiety is the high potential flavin that serves as the one-electron reductant for cytochrome 1 450 ... 

Cytochromes are used in the conversion of cholesterol to the steroid hormones. Iliese hormones include aldosterone, cortisol, and the sex hormones. Synthesis of aldosterone, for example, occurs in the mitochondria of the adrenal cortex. One of the steps in aidostero ne synthesis is a hydroxylation that is cataly .ed by a complex of adrenodoxin reductase (FAD-containing protein), adrenodoxin (nonheme iron protein), and cytochrome P450 (heme protein). 

Cytochrome P450 monooxygenases contain a heme prosthetic group and require electrons for their activity. In the P450 catalytic cycle, two consecutive electron-transfer... 

Some of the major enzyme groups that facilitate this transformation are heme-containing MOs of the cytochrome P450 type [111], alkane hydroxylases, xylene monooxygenases, styrene monooxygenases [105], and haloperoxidases [112],... 

Isoforms of Cytochrome P450 Make Up a Superfamily of Heme-Containing Enzymes... 

Peroxidases are heme iron-containing proteins similar in structure to that of cytochromes P450. The major difference is that peroxidases have histidine as the axial ligand instead of cysteine, and there are also other polar amino acids close to the heme iron that help to catalyze the peroxidase function of the enzyme (41). The result is that the peroxidases very rapidly catalyze the reduction of hydroperoxides to alcohols (or water in the case of... 

The enzymes of this type that have been characterized contain some type of redox-active cofactor, such as a flavin (3), or a metal ion (heme iron, non-heme iron, or copper), or both (4-6). Our understanding of the mechanism of these enzymes is most advanced in the case of the heme-containing enzyme cytochrome P450. But in spite of the availability of a crystal structure of an enzyme-substrate complex (7) and extensive information about related reactions of low molecular weight synthetic analogues of cytochrome P450 (8), a detailed picture of the molecular events that are referred to as "dioxygen activation" continues to elude us. 

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