▁of ▁the ▁Ohio ▁House ▁of ▁Representatives <0x0A> </s> ▁P orph obil in ogen ▁is ▁an ▁organ ic ▁comp ound ▁that ▁occurs ▁in ▁living ▁organ isms ▁as ▁an ▁intermediate ▁in ▁the ▁b ios yn thesis ▁of ▁por ph yr ins , ▁which ▁include ▁critical ▁subst ances ▁like ▁hem og lo bin ▁and ▁ch lor oph yll . ▁ ▁The ▁name ▁is ▁often ▁abbre vi ated ▁P B G . ▁ ▁The ▁structure ▁of ▁the ▁mole c ule ▁can ▁be ▁described ▁as ▁mole c ule ▁of ▁p yr role ▁with ▁side ch ains ▁subst it uted ▁for ▁hydro gen ▁atoms ▁at ▁positions ▁ 2 , ▁ 3 ▁and ▁ 4 ▁in ▁the ▁ring ▁( 1 ▁being ▁the ▁nit ro gen ▁atom ); ▁respectively , ▁an ▁am in om eth yl ▁group ▁, ▁an ▁ac etic ▁acid ▁( car box ym eth yl ) ▁group ▁, ▁and ▁a ▁prop ionic ▁acid ▁( car box y eth yl ) ▁group ▁. ▁ ▁B ios yn thesis ▁In ▁the ▁first ▁step ▁of ▁the ▁por ph yr in ▁b ios yn thesis ▁path way , ▁por ph obil in ogen ▁is ▁generated ▁from ▁am in ole v ul inate ▁( AL A ) ▁by ▁the ▁en zym e ▁A LA ▁de h yd rat ase . ▁ ▁Met abol ism ▁In ▁the ▁typical ▁por ph yr in ▁b ios yn thesis ▁path way , ▁four ▁mole cules ▁of ▁por ph obil in ogen ▁are ▁concaten ated ▁by ▁car b ons ▁ 2 ▁and ▁ 5 ▁of ▁the ▁p yr