. ▁ ▁Chem ical ▁structures ▁ ▁Some ▁examples ▁of ▁str ig ol act ones ▁include : ▁ ▁B ios yn thesis ▁ ▁Car oten oid ▁path way ▁via ▁car la ct one ▁ ▁The ▁b ios yn th etic ▁path way ▁of ▁the ▁str ig ol act ones ▁has ▁not ▁been ▁fully ▁el uc id ated , ▁but ▁different ▁steps ▁have ▁been ▁identified , ▁including ▁the ▁required ▁en zym es ▁to ▁carry ▁out ▁the ▁chemical ▁transformation . ▁The ▁first ▁step ▁is ▁the ▁is omer ization ▁of ▁the ▁ 9 th ▁chemical ▁bond ▁of ▁the ▁- car ot ene , ▁changing ▁from ▁trans ▁configuration ▁to ▁c is . ▁This ▁first ▁step ▁is ▁carried ▁out ▁by ▁the ▁en zym e ▁- car ot ene ▁is omer ase , ▁also ▁called ▁D W AR F 2 7 ▁or ▁D 2 7 ▁for ▁short , ▁which ▁required ▁iron ▁as ▁a ▁c of actor . ▁The ▁second ▁step ▁is ▁the ▁chemical ▁separation ▁of ▁ 9 - cis -- car ot ene ▁into ▁two ▁different ▁comp ounds : ▁ ▁the ▁first ▁one ▁is ▁ 9 - cis - al de hy de ▁and ▁the ▁second ▁is ▁- ion one . ▁This ▁second ▁step ▁is ▁catal ized ▁by ▁the ▁car oten oid ▁cle av age ▁de ox y gen ase ▁ 7 ▁( CC D 7 ). ▁In ▁the ▁third ▁step , ▁another ▁car oten oid ▁cle av age ▁o xygen ase , ▁called ▁C CD 8 ▁( from ▁the ▁same ▁family ▁as ▁C CD 7 ), ▁catal y ze