▁action ▁ ▁P 4 5 0 s cc ▁catal y zes ▁the ▁conversion ▁of ▁ch ol ester ol ▁to ▁preg nen ol one ▁in ▁three ▁mon o ox y gen ase ▁re actions . ▁These ▁involve ▁ 2 ▁hydro x yl ations ▁of ▁the ▁ch ol ester ol ▁side - chain , ▁which ▁generate , ▁first , ▁ 2 2 R - h ydro x ych ol ester ol ▁and ▁then ▁ 2 0 alpha , 2 2 R - d ih ydro x ych ol ester ol . ▁ ▁The ▁final ▁step ▁cle aves ▁the ▁bond ▁between ▁car b ons ▁ 2 0 ▁and ▁ 2 2 , ▁resulting ▁in ▁the ▁production ▁of ▁preg nen ol one ▁and ▁is oc ap ro ic ▁al de hy de . ▁ ▁Each ▁mon o ox y gen ase ▁step ▁requires ▁ 2 ▁electrons ▁( redu cing ▁equival ents ). ▁The ▁initial ▁source ▁of ▁the ▁electrons ▁is ▁N AD PH . ▁The ▁electrons ▁are ▁transferred ▁from ▁N AD PH ▁to ▁P 4 5 0 s cc ▁via ▁two ▁electron ▁transfer ▁prote ins : ▁ad ren odox in ▁re duct ase ▁and ▁ad ren odox in . ▁ ▁All ▁three ▁prote ins ▁together ▁const itute ▁the ▁ch ol ester ol ▁side - chain ▁cle av age ▁complex . ▁ ▁The ▁invol vement ▁of ▁three ▁prote ins ▁in ▁ch ol ester ol ▁side - chain ▁cle av age ▁reaction ▁ra ises ▁the ▁question ▁of ▁whether ▁the ▁three ▁prote ins ▁function ▁as ▁a ▁t ern ary ▁complex ▁as