Atypical cytochrome P450 involved in brassinosteroids (BRs) inactivation and regulation of BRs homeostasis. Does not possess carbon 26 hydroxylase activity and may inactivate BRs by hydroxylation of carbons other than C-26. Acts in association with CYP734A1 to inactivate BRs and modulate photomorphogenesis. Expressed in hypocotyls, roots, cotyledons, stamens and silique junctions. By brassinolide (BL), auxin and dark treatment. No visible phenotype under normal growth condition, but increased length of dark-grown hypocotyls, reduced responsiveness of hypocotyls to light and increased responsiveness to brassinolide (BL). The gain-of-function mutant shk1-D (T-DNA tagging) shows a severe dwarf phenotype and an important reduction of the levels of the BRs castasterone (CS), 6-deoxocastasterone (6-deoxoCS) and 6-deoxotyphasterol (6-deoxoTY). The gain-of-function mutant chi2 show reduced length of hypocotyls grown in red, far-red and blue lights or darkeness. The gain of function mutant dlf1-D shows severe dwarf phenotype with low fertility. Belongs to the cytochrome P450 family.