Aggregation of Phosphates Enhances Enzyme Activity in Aqueous Solution

Diffusion coefficients and viscosities of tetrabutylammonium dihydrogen phosphate ([NBu4]+[H2PO4]−), potassium dihydrogen phosphate (K+[H2PO4]−), tetrabutylammonium bromide ([NBu4]+[Br]−), tetrabutylammonium chloride ([NBu4]+[Cl]−) and biologically relevant phosphate salts including adenosine monophosphate (AMP), adenosine diphosphate (ADP) and adenosine triphosphate (ATP) were measured in aqueous solutions as a function of concentration across millimolar concentrations. The [NBu4]+ cation makes the solutions viscous at high millimolar concentrations, and there was no significant evidence of aggregation of the [H2PO4]− anion. At higher millimolar concentrations, ATP, ADP and AMP aggregate in aqueous solutions. The increasing concentration of ATP and ADP leads to increased activity of three different enzymes: cytochrome c, laccase, and horseradish peroxidase.