Steady-state kinetics of laccasse from Rhus vernicifera

The steady-state kinetics of laccasse (monophenol, dihydroxyphenylalanine: oxygen oxidoreductase, EC 1.14.18.1) from the lacquer tree Rhus vernicifera is investigated using the respirograph method to produce Lineweaver-Burk plots of oxygen consumption rate against oxygen concentration. A ping-pong mechanisms is established. The kinetic constants obtained according to the model is in close agreement with the corresponding values obtained from earlier studies on the transient reactions between the reduced enzyme and oxygen (Andréasson, L.E., Brändén, R. and Reinhammar, B. (1976) Biochim. Biophys. Acta 438, 370--379) and between the oxidized enzyme and reducing substrates (Andréasson, L.E. and Reinhammar, B. (1976) Biochim. Biophys. Acta 445, 579--597).