| Group | ||
| Adrenodoxin family | 31 | 14 K |
| Adrenodoxin reductases | 7 | 4 K |
| Cytochrome b5 reductases | 27 | 15 K |
| Cytochromes b5 | 51 | 25 K |
| Fe3S4 ferredoxins | 7 | 3 K |
| NADH:ferredoxin reductases | 3 | 2 K |
| NADPH:P450 reductases | 22 | 11 K |
| P450 | 807 | 361 K |
Homologues of components of P450-containing systems | ||
| Group | ||
| Alkyl hydroperoxide reductases | 18 | 7 K |
| Cytochrome b5 domain-containing proteins | 67 | 30 K |
| Dihydrolipoamide dehydrogenases | 67 | 27 K |
| Ferredoxin:NADP+ reductases | 31 | 15 K |
| Flavodoxins | 63 | 28 K |
| Glutathione reductases | 30 | 15 K |
| Mercuric reductases | 13 | 5 K |
| NADPH:sulphite reductases flavoprotein | 46 | 17 K |
| Nitric Oxide Synthases | 35 | 29 K |
| Plant and fungal nitrate reductases | 36 | 14 K |
| Thioredoxin reductases | 75 | 31 K |
| Trypanothione reductases | 5 | 3 K |