s ▁in hib ition ▁while ▁PR PP ▁is ▁in ▁large ▁amount ▁bind s ▁to ▁the ▁en zym e ▁which ▁causes ▁activation . ▁ ▁So ▁I MP , ▁G MP ▁and ▁A MP ▁are ▁in hib itors ▁while ▁PR PP ▁is ▁an ▁activ ator . ▁Between ▁the ▁formation ▁of ▁ 5 '- ph osph or ib os yl , ▁am ino im id az ole ▁and ▁I MP , ▁there ▁is ▁no ▁known ▁reg ulation ▁step . ▁ ▁Salv age ▁Pur ines ▁from ▁turn over ▁of ▁cell ular ▁nucle ic ▁ac ids ▁( or ▁from ▁food ) ▁can ▁also ▁be ▁salv aged ▁and ▁re used ▁in ▁new ▁nucle ot ides . ▁▁ ▁The ▁en zym e ▁ad en ine ▁ph osph or ib os yl trans fer ase ▁( AP RT ) ▁salv ages ▁ad en ine . ▁▁ ▁The ▁en zym e ▁hy po x anth ine - gu an ine ▁ph osph or ib os yl trans fer ase ▁( H G PR T ) ▁salv ages ▁gu an ine ▁and ▁hy po x anth ine . ▁( Gen etic ▁def ic iency ▁of ▁H G PR T ▁causes ▁L esch – N y han ▁synd rome .) ▁ ▁Dis orders ▁When ▁a ▁defect ive ▁gene ▁causes ▁g aps ▁to ▁appear ▁in ▁the ▁met abol ic ▁rec y cling ▁process ▁for ▁pur ines ▁and ▁p yr im id ines , ▁these ▁chemical s ▁are ▁not ▁met abol ised ▁properly , ▁and ▁adult s ▁or ▁children ▁can ▁suffer ▁from ▁any ▁one ▁of ▁twenty