Cytochrome P450 involved in brassinosteroids (BRs) inactivation and regulation of BRs homeostasis. Is a multifunctional and multisubstrate enzyme that controls the endogenous bioactive BR content both by direct inactivation of castasterone (CS) and by decreasing the levels of BR precursors. Catalyzes the oxidation of carbon 22 hydroxylated BR intermediates to produce C26 oxidized metabolites. Highly expressed in leaf sheaths. Expressed in roots, shoot apex, leaf blades, internodes and panicles. By brassinolide (BL). Plants overexpressing CYP734A6 show a dwarf phenotype, characterized by abnormal leaves with stiff, tortuous blades, undeveloped leaf sheaths, no flowering and bear seeds. Over-expression of CYP734A6 causes an important reduction of the levels of the BRs castasterone (CS), 6-deoxocastasterone (6-deoxoCS) and 6-deoxotyphasterol (6-deoxoTY). Belongs to the cytochrome P450 family.