Change in the Ultraviolet Absorption of an Adenosine Triphosphate Analog, β-Naphthyl Triphosphate, during Its Hydrolysis by Heavy Meromyosin1

Abstract

It was found that the absorption spectrum of β-naphthyl triphosphate is different from that of β-naphthyl diphosphate in the range 290–335 nm. Thus, β-naphthyl triphosphate hydrolysis by heavy meromyosin can be recorded continuously as a function of time by means of a spectrophotometer. By analyzing the time course, the apparent kinetic parameters were easily and rapidly obtained. If necessary, the true kinetic parameters, including the product dissociation constants, can be estimated spectrophotometrically. β-Naphthyl triphosphate hydrolysis was inhibited competitively by ATP. By analyzing the time course, it was, therefore, possible to estimate the kinetic parameters of ATP hydrolysis indirectly, and reasonable values were obtained. β-Naphthyl triphosphate hydrolysis by heavy meromyosin was performed under various conditions. Unlike that of ATP, the hydrolysis of β-naphthyl triphosphate was inhibited monotonously by treatment of heavy meromyosin with p-hydroxy-mercuribenzoate.