KINETICS OF BIOLUMINESCENCE IN THE FIREFLY LUCIFERIN LUCIFERASE SYSTEM

The kinetics of enzymatic oxidation of firefly luciferin over a wide t ime range (from milliseconds to hours) was investigated at varied init ial concentrations of luciferase and its substrates (luciferin and ATP ). A kinetic model was developed and the rate constants for the elemen tary reaction steps were determined from ''fast'' and ''integral'' kin etic data. Some constants were estimated by computer simulation, resul ting in a fair agreement between the calculated and observed progress curves. According to the model proposed, the initial flash is due to a first turnover of the enzyme, and the low light emission that follows is limited by slow dissociation of the enzyme-product complex. Inacti vation of the enzyme and of its complexes with the substrates and the products is responsible for the gradual decrease in light intensity do wn to tao during the course of the reaction.