Inosine diphosphatase (nucleoside diphosphatase) from mammalian tissues

Abstract

The discovery of this enzyme was announced almost simultaneously from several laboratories^1–4. Strominger, et al.¹ found that a water extract of calf liver acetone powder dephosphorylated uridine triphosphate 50 times faster than adenosine triphosphate. Evidence was presented that the dephosphorylation of uridine triphosphate occurred by a series of reactions involving the enzymes adenosine triphosphate-uridine monophosphate transphorylase, nucleoside diphosphokinase, and adenosine triphosphate-adenosine monophosphate transphosphorylase, as well as a new phosphatase which hydrolyzed uridine diphosphate to uridine monophosphate and orthophosphate. Plaut ² detected a similar phosphatase in aqueous extracts of acetone desiccated mitochondria from rat liver, and of acetone powders of washed residues from beef liver. Studies with the purified enzyme from beef liver showed that inosine dinhosnhate is hydrolyzed to 5′-inosinic acid and orthophosphate.