FE(III)-ION-CATALYZED NONENZYMATIC TRANSFORMATION OF ADENOSINE-DIPHOSPHATE INTO ADENOSINE-TRIPHOSPHATE .2. EVIDENCE OF CATALYTIC NATURE OF FE IONS

Non-enzymatic phosphorylation of adenosine diphosphate (ADP) to adenosine triphosphate (ATP) in aqueous solutions using acetyl phosphate has been studied extensively. The reaction proceeds in the presence of Fe(III) ions. Normally, the yield of ATP never exceeds the amount of Fe ions but, when a sufficient amount of Mg(II) ions is added to the reaction system, the yield of ATP increases beyond the amount of Fe ions. This is because the Fe(III) ion is tightly bound to not only ADP but also ATP, the phosphorylation product. When, however, the Fe(III) ion is liberated from ATP by exchanging with an Mg(II) ion, it regains catalytic activity and contributes to the surplus production of ATP. The Fe(III) ion with either a single molecule of 1,10-phenanthroline or 2,2'-bipyridyl exhibits a remarkably high catalytic activity. This suggests that the Fe(II) aquo ion should also be an excellent catalyst.