The Regulation of Purine Utilization in Bacteria

The adenine phosphoribosyltransferase of Escherichia coli K-12 is markedly derepressed under cultural conditions which preclude de nova synthesis of purines.The enzyme obtained from such cultures was purified to constant specific activity of 14.0 pmoles of AMP formed at 37" per min per mg.Enzyme activity is associated with an apparently homogeneous protein species as indicated by either acrylamide gel electrophoresis or gel filtration at low pH and in the presence of divalent cation.The molecular weight as estimated by gel filtration under these conditions is 40,000.At high pH and in the absence of divalent cations, several protein moieties are observed by these techniques; each, however, exhibits enzyme activity.Apparent K, values were found to be 0.01