The catalytic effect of molybdate on the hydrolysis of organic phosphates.

The increased rate of hydrolysis of organic phosphate compounds in the presence of molybdate has been observed frequently and is the basis for the estimation of phosphocreatine (1) and acetyl phosphate (2) in tissue extracts. A study was undertaken to determine whether this was a general effect and, if so, to elucidate the mechanism. While these experiments were in progress, Weil-Malherbe and Green (3) reported a study of the catalytic effect of molybdate on the hydrolysis of a series of phosphate compounds. Their findings were that (o) the effect increases with increasing molybdate concentration; (b) the effect increases exponentially with increasing temperature; (c) there is a distinct pH optimum for the catalytic activity for each compound; and (cl) the hydrolysis shows the kinetics of a first order reaction both in the presence and in the absence of mo1ybdat.e. We have studied a similar series of compounds, varying widely in their lability to hydrolysis by acid. Molybdate was found to catalyze the hydrolysis of all the substances investigated, both alone and in the presence of acid. The catalysis has been shown to be accompanied by the formation of a molybdate-organic phosphate complex. This complex has the same blue color as does reduced phosphomolybdate. Furthermore, it reacts with the bisulfite-aminonaphtholsulfonic acid reagent in a manner similar to phosphomolybdate to give additional amounts of the blue color. The analytical methods used by Weil-Malherbe and Green therefore do not make possible a distinction between the complex and its hydrolysis products. The calculated kinetics reported by these workers consequently may lack significance.