FACTORS AFFECTING THE KINETICS OF LIGHT-EMISSION FROM CRUDE AND PURIFIED FIREFLY LUCIFERASE

Crude and purified firefly luciferase was used to assay ATP from 0.2 pmol-2 .mu.mol. Over this range of ATP concentrations there is a large change in the kinetics of light emission. At the lowest concentrations of ATP, light emission rises to a maximum and remains constant for a minute or longer. As the concentration of ATP is increased, the peak light intensity increases and the decay rate of light increases significantly. This is true for both the crude and the purified enzyme. High concentration of sodium arsenate and other salts inhibit the peak light emission and prevent the decay in light intensity which is due to product inhibition. Almost any type of kinetics can be obtained by manipulating the experimental conditions.