Catalyzes the C6-oxidation step and lactonization in brassinosteroids biosynthesis (PubMed:15710611). Converts 6-deoxocastasterone (6-deoxoCS) to castasterone (CS), and castasterone to brassinolide (BL) (PubMed:15710611). May also convert 6-deoxoteasterone (6-deoxoTE) to teasterone (TE), 3-dehydro-6-deoxoteasterone (6-deoxo3DT, 6-deoxo-3-DHT) to 3-dehydroteasterone (3DT, 3-DHT), and 6-deoxotyphasterol (6-deoxoTY) to typhasterol (TY). Seems also able to convert teasterone (TE) and typhasterol (TY) to 7-oxateasterone (7-OXTE) and 7-oxatyphasterol (7-OXTY), respectively (PubMed:18685225). Catalyzes the conversion of 6-deoxo-28-norteasterone (6-deoxo-28-norTE) to 28-norteasterone (28-norTE), 6-deoxo-28-nordeoxoteasterone (6-deoxo-28-nor-3-DHT) to 28-nordeoxoteasterone (28-nor-3-DHT), 6-deoxo-28-nortyphasterol (6-deoxo-28-norTY) to 28-nortyphasterol (28-norTY) and 6-deoxo-28-norcastasterone (6-deoxo-28-norCS) to 28-norcastasterone (28-norCS) (PubMed:22170941). Involved in a negative regulation of responses to abscisic acid (ABA) and drought tolerance (PubMed:27455172). 6-deoxoteasterone + O2 + reduced [NADPH--hemoprotein reductase] = 6alpha-hydroxyteasterone + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 6alpha-hydroxytyphasterol + O2 + reduced [NADPH--hemoprotein reductase] = H(+) + 2 H2O + oxidized [NADPH--hemoprotein reductase] + teasterone 3-dehydro-6-deoxoteasterone + O2 + reduced [NADPH--hemoprotein reductase] = 3-dehydro-6alpha-hydroxyteasterone + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 3-dehydro-6alpha-hydroxyteasterone + O2 + reduced [NADPH--hemoprotein reductase] = 3-dehydroteasterone + H(+) + 2 H2O + oxidized [NADPH--hemoprotein reductase] 6-deoxotyphasterol + O2 + reduced [NADPH--hemoprotein reductase] = 6alpha-hydroxytyphasterol + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 6alpha-hydroxytyphasterol + O2 + reduced [NADPH--hemoprotein reductase] = H(+) + 2 H2O + oxidized [NADPH--hemoprotein reductase] + typhasterol 6-deoxocastasterone + O2 + reduced [NADPH--hemoprotein reductase] = 6alpha-hydroxycastasterone + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 6alpha-hydroxycastasterone + O2 + reduced [NADPH--hemoprotein reductase] = castasterone + H(+) + 2 H2O + oxidized [NADPH--hemoprotein reductase] castasterone + O2 + reduced [NADPH--hemoprotein reductase] = brassinolide + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 3-dehydro-6-deoxoteasterone + 2 O2 + 2 reduced [NADPH--hemoprotein reductase] = 3-dehydroteasterone + 2 H(+) + 3 H2O + 2 oxidized [NADPH--hemoprotein reductase] 6-deoxocastasterone + 2 O2 + 2 reduced [NADPH--hemoprotein reductase] = castasterone + 2 H(+) + 3 H2O + 2 oxidized [NADPH--hemoprotein reductase] 6-deoxoteasterone + 2 O2 + 2 reduced [NADPH--hemoprotein reductase] = 2 H(+) + 3 H2O + 2 oxidized [NADPH--hemoprotein reductase] + teasterone 6-deoxotyphasterol + 2 O2 + 2 reduced [NADPH--hemoprotein reductase] = 2 H(+) + 3 H2O + 2 oxidized [NADPH--hemoprotein reductase] + typhasterol 6-deoxo-28-norteasterone + 2 O2 + 2 reduced [NADPH--hemoprotein reductase] = 28-norteasterone + 2 H(+) + 3 H2O + 2 oxidized [NADPH--hemoprotein reductase] 6-deoxo-28-norteasterone + O2 + reduced [NADPH--hemoprotein reductase] = 6alpha-hydroxy-28-norteasterone + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 6alpha-hydroxy-28-norteasterone + O2 + reduced [NADPH--hemoprotein reductase] = 28-norteasterone + H(+) + 2 H2O + oxidized [NADPH--hemoprotein reductase] 6-deoxo-28-nortyphasterol + 2 O2 + 2 reduced [NADPH--hemoprotein reductase] = 28-nortyphasterol + 2 H(+) + 3 H2O + 2 oxidized [NADPH--hemoprotein reductase] 6-deoxo-28-nortyphasterol + O2 + reduced [NADPH--hemoprotein reductase] = 6alpha-hydroxy-28-nortyphasterol + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 6alpha-hydroxy-28-nortyphasterol + O2 + reduced [NADPH--hemoprotein reductase] = 28-nortyphasterol + H(+) + 2 H2O + oxidized [NADPH--hemoprotein reductase] 6-deoxo-28-norcastasterone + 2 O2 + 2 reduced [NADPH--hemoprotein reductase] = 28-norcastasterone + 2 H(+) + 3 H2O + 2 oxidized [NADPH--hemoprotein reductase] 6-deoxo-28-norcastasterone + O2 + reduced [NADPH--hemoprotein reductase] = 6alpha-hydroxy-28-norcastasterone + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 6alpha-hydroxy-28-norcastasterone + O2 + reduced [NADPH--hemoprotein reductase] = 28-norcastasterone + H(+) + 2 H2O + oxidized [NADPH--hemoprotein reductase] 3-dehydro-6-deoxo-28-norteasterone + 2 O2 + 2 reduced [NADPH--hemoprotein reductase] = 6-dehydro-28-norteasterone + 2 H(+) + 3 H2O + 2 oxidized [NADPH--hemoprotein reductase] 3-dehydro-6-deoxo-28-norteasterone + O2 + reduced [NADPH--hemoprotein reductase] = 3-dehydro-6alpha-hydroxy-28-norteasterone + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 3-dehydro-6alpha-hydroxy-28-norteasterone + O2 + reduced [NADPH--hemoprotein reductase] = 6-dehydro-28-norteasterone + H(+) + 2 H2O + oxidized [NADPH--hemoprotein reductase] Plant hormone biosynthesis; brassinosteroid biosynthesis. Concentrates in endoplasmic reticulum subdomains adjacent to chloroplasts when farnesylated. Expressed in stems, hypocotyls, leaves, siliques, shoots, and roots, with a higher expression in apical shoots. Repressed by brassinolide (BL) treatment (PubMed:12529536). Induced rapidly and transiently in seedlings hooks, petioles and cotyledons but fades out of hypocotyls after exposure to light (PubMed:32333772). Isoprenylated (farnesylated); this addition of a 15-carbon farnesyl isoprenoid to the carboxy terminus is required for endoplasmic reticulum localization and essential for the biosynthesis of brassinolide. Reduced brassinolide accumulation but increased responsiveness to abscisic acid (ABA) and overall drought tolerance. Belongs to the cytochrome P450 family. Truncated N-terminus.