The mechanism of reaction of adenine phosphoribosyltransferase 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 aden...

A quantitative method for the study of the kinetics of immune hemolysis is described. In the presence of excess C' and limited amounts of antibody the kinetics of hemolysis resemble those of enzymatic processes. Assays of hemolytic antibody should therefore be based on velocity measurements rather than end point titrations.