Enzymatic Synthesis of Nucleoside Triphosphates. Does It Involve An Ion-Radical Path ?

Abstract

Accumulation and release of energy in the nucleoside triphosphate enzymatic synthesis and hydrolysis does not limited to a routine energy consuming nucleophilic mechanism. These processes require an overcoming the large energy barrier exceeding a total value of accumulated or released energy level by at least 3 – 4 times (~10 kcal/mol). This energy is supposed to be taken from the mechanical compression of the catalytic site and used to form P–O chemical bond by a direct nucleophilic addition of phosphate to nucleoside diphosphate (ADP as an example). A new, energetically “cheapâ€, ion-radical mechanism of the ATP biosynthesis has been proposed due to the observation of magnetic isotope and magnetic field effects on the ATP synthesis. This mechanism is about to generate  a compression energy to “spend†on a partial dehydratation of magnesium ion inside the nucleotidyl transferase catalyric site (energy cost of this process is 3-5 kcal/mol, i.e. by 2-3 times less than a total accumulated or released energy). Dehydration of this ion is to increase its electron affinity and hence to stimulate an electron transfer from ADP^3- to Mg²⁺. This reaction is a starting point of the ion-radical mechanism considering the molecular mechanics of enzymatic machines and its quantum chemistry background as well. To the contrast of a hardly controllable nucleophilic path, the ion-radical mechanism might be turned on/off  by a targeted delivery of  paramagnetic magnesium ions, ²⁵Mg²⁺, towards the phosphate transferring enzyme catalytic site. The magnesium isotope substitution is easily reachable by the endo-osmotic pressure techniques, which makes it attractive for further biotechnological and/or pharmacological application(s).