Kinetic Studies of Adenine Phosphoribosyltransferase

Abstract

Abstract The mechanism of reaction of adenine phosphoribosyl-transferase from Ehrlich ascites tumor cells was investigated kinetically by initial velocity and product inhibition studies. The data are consistent with a mechanism in which 5-phosphoribosylpyrophosphate reacts with the enzyme to form an intermediate, presumably an enzyme-ribose 5-phosphate complex, with which adenine then reacts to form adenylate. Noncompetitive inhibition by inorganic pyrophosphate with respect to adenine suggests that the former binds tightly to the enzyme-adenylate complex. Both PP-ribose-P and PPi participate in the form of their magnesium complexes.