ton ates ▁a ▁water ▁mole c ule , ▁which ▁can ▁then ▁perform ▁a ▁nucle oph il ic ▁attack ▁on ▁the ▁ph osph ate ▁group ▁located ▁ 5 ´ ▁to ▁the ▁AP ▁site . ▁Next , ▁electrons ▁from ▁one ▁of ▁the ▁o xygen ▁atom ▁in ▁the ▁ph osph ate ▁group ▁moves ▁down , ▁kick ing ▁off ▁one ▁of ▁the ▁other ▁o xygen ▁to ▁create ▁a ▁free ▁ 5 ´ ▁ph osph ate ▁group ▁on ▁the ▁AP ▁site ▁and ▁a ▁free ▁ 3 ´ - OH ▁on ▁the ▁normal ▁nucle ot ide , ▁both ▁of ▁which ▁are ▁stabil ized ▁by ▁the ▁M g 2 + ▁ion . ▁ ▁In hib ition ▁of ▁A PE 1 ▁ ▁Kn own ▁in hib itors ▁of ▁A PE 1 ▁include ▁ 7 - nit ro ind ole - 2 - car box y lic ▁acid ▁( N CA ) ▁and ▁luc anth one . ▁Both ▁of ▁these ▁structures ▁possess ▁rings ▁attached ▁to ▁short ▁ch ains , ▁which ▁appear ▁similar ▁to ▁the ▁de ox y ri bose ▁sugar ▁ring ▁without ▁a ▁base ▁attached ▁and ▁ph osph odi ester ▁bond ▁in ▁DNA . ▁Further , ▁both ▁contain ▁many ▁H - b ond ▁accept ors ▁which ▁may ▁interact ▁with ▁the ▁H - b ond ▁don ors ▁in ▁the ▁active ▁site ▁of ▁A PE 1 , ▁causing ▁these ▁in hib itors ▁to ▁stick ▁in ▁the ▁active ▁site ▁and ▁prevent ing ▁the ▁en zym e ▁from ▁catal yz ing ▁other ▁re actions . ▁ ▁A PE 1 ▁as ▁chem op re vent ive ▁target