cytochrome P450 families 77 and 89, and similar cytochrome P450s
This group includes cytochrome P450 families 73 (CYP77) and 89 (CYP89), which are sister families that share a common ancestor. CYP89, present only in angiosperms, is younger than CYP77, which is already found in lycopods; thus, CYP89 may have evolved from CYP77 after duplication and divergence. Also included in this group is ent-kaurene oxidase, called CYP701A3 in Arabidopsis thaliana and CYP701B1 in Physcomitrella patens, that catalyzes the oxidation of ent-kaurene to form ent-kaurenoic acid. CYP701A3 is sensitive to inhibitor uniconazole-P while CYP701B1 is not. This CYP77/89 group belongs to the large cytochrome P450 (P450, CYP) superfamily of heme-containing proteins that catalyze a variety of oxidative reactions of a large number of structurally different endogenous and exogenous compounds in organisms from all major domains of life. CYPs bind their diverse ligands in a buried, hydrophobic active site, which is accessed through a substrate access channel formed by two flexible helices and their connecting loop.