Steady-state kinetics of 3-mercaptopyruvate sulfurtransferase from bovine kidney

Mammalian 3-mercaptopyruvate sulfurtransferase (EC 2.8.1.2), purified to apparent homogeneity by a new procedure, was studied by steady-state kinetic methods. The enzyme-catalyzed transfer of a sulfur atom from 3-mercaptopyruvate either to 2-mercaptoethanol or to a second molecule of 3-mercaptopyruvate was found to proceed by a sequential formal mechanism. An overall mechanism incorporating both of these transfers was shown to be capable of generating all of the initial velocity and product inhibition behavior observed.