Formation of Inosine-5′-Monophosphate by a Kinase in Cell-Free Extracts of Ehrlich Ascites Cells in Vitro ∗

Abstract

Summary

Cell-free extracts from Ehrlich ascites tumor cells were found to convert inosine to inosine 5′-monophosphate at a rate comparable to the conversion of adenosine to adenosine 5′-monophosphate by the same extracts. This inosine kinase appeared to be distinct from adenosine kinase. Conditions necessary for optimum activity were studied. Magnesium ions were required, as was a relatively low level of ATP and an ATP-regenerating system. The pH optimum was approximately 7.4.