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QuickView for P450s (biogroup)
- Description:
- P450 enzymes constitute a superfamily of haem-thiolate proteins, widely distributed in bacteria, fungi, plants and animals. The enzymes are involved in metabolism of a plethora of both exogenous and endogenous compounds. Usually, they act as terminal oxidases in multi-component electron-transfer chains, called P450-containing monooxygenase systems. On the basis of sequence similarity, all P450s can be categorised into 2 main classes, the so-called B- and E-classes: P450 proteins of prokaryotic 3-component systems and fungal P450nor (CYP55) belong to the B-class; all other known P450s from distinct systems are of the E-class. E-class P450s may be further divided into 5 subclasses (groups) according to protein sequence similarities. The data suggest that divergence of the P450 superfamily into B- and E-classes, and further divergence into stable P450 groups within the E-class, must be very ancient and had occurred before the appearance of eukaryotes. Given the rapid increase in numbers of P450s, Nelson introduced the concept of a higher-order classification of P450 families into clans based on sequence similarity. This is similar to the previous grouping into B- and E-classes; both classifications are still used. According to Nelsons system, clan 2 contains the CYP2 plus CYP1, 17, 18, 21 and 71 families, and corresponds to the E-class group I proteins. Members of the first 4 families are of vertebrate origin, while those from CYP71 derive from plants. CYP1 and CYP2 enzymes mainly metabolise exogenous substrates, whereas CYP17 and CYP21 are involved in metabolism of endogenous physiologically-active compounds. This entry represents the CYP2 family, comprising 15 subfamilies (A-H, J-N, P and Q), is the most dominant in clan 2. Six of these subfamilies are non-mammalian: 2H derives from chicken; 2K, 2M, 2N and 2P are from fish; 2L is from lobster; and 2Q from Xenopus. The first five (A-E) are present in mammalian liver, but in differing amounts and with different inducibilities. Members of the CYP2F gene subfamily, meanwhile, are selectively expressed in lung tissues, and have been implicated as important catalysts in the formation of reactive intermediates from several pneumotoxic chemicals. Human CYP2F1 bioactivates 3-methylindole (3MI), while mouse CYP2F2 bioactivates naphthalene.
- Taxonomy/Path:
- InterPro : Cytochrome P450, E-class, CYP24A, mitochondrial / Cytochrome P450, CYP2 family
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