Adenosine-5′-sulfatopyrophosphate, an analogue of adenosine triphosphate: I. Preparation, properties, and mode of cleavage by snake venoms

Abstract

An improved and simplified procedure has been worked out for the synthesis and isolation of adenosine-5′-sulfatopyrophosphate, a sulfate analogue of adenosine triphosphate. The sulfate analogue has two isomeric forms in which the sulfate grouping is on either the α- or β-phosphates of adenosine diphosphate. The apparent formation constants of adenosine-5′-sulfatopyrophosphate (mixed isomers) and adenosine-5′-sulfatophosphate with Mg ++ and Ca ++ have been measured. These values are low but comparable to similar constants measured by other workers for the trianionic form of adenosine triphosphate and the dianionic form of adenosine diphosphate, respectively. Both isomers of the sulfate analogue are cleaved by enzymes from the venom of Crotalus atrox and Vipera russellii. Phosphosulfate has been identified as one of the products indicating cleavage between the two phosphate groupings. A similar type of cleavage appears to be catalyzed by an acetone powder of Escherichia coli; E. coli alkaline phosphatase, however, has no effect on the analogue. Crude potato apyrase slowly hydrolyzes the sulfate analogue but apparently by an enzyme other than the apyrase. Enzyme-free controls in almost every case were stable, some for periods as long as 54 hours at 25 °C and pH 8. This stability is in marked contrast to previously published results, and work reported here indicates the analogue is suitable for enzymic studies.