The Regulation of Purine Utilization in Bacteria

The uptake of adenine by membrane vesicles of Escherichia coli is accompanied by its conversion to AMP and is stimulated by P-ribose-PP.The pH optimum for uptake in phosphate buffer is 7.8.The K,,, for adenine is 20 pM and for P-ribose-PP is 200 pM.Uptake is inhibited by AMP and ATP.Adenine phosphoribosyltransferase activity is associated with membrane vesicles.A role of this enzyme in the uptake of adenine is indicated by the fact that the uptake and enzyme activity are similarly affected by variations in pH, substrates, and inhibitors; moreover, removal of the enzyme from the vesicles results in a concomitant loss of uptake activity.The enzyme isolated from membrane vesicles appears to be identical with the soluble enzyme isolated directly from cell-free extracts.