This is an alternative activity of the firefly luciferase (EC?1.13.12.7), which the enzyme exhibits under normal conditions only when acting on the?L-enantiomer of its substrate. The?D-isomer can act as a substrate for the CoA¡ªligase activity?in vitro?only under low oxygen conditions that are not found?in vivo. The activation of?L-firefly luciferin to a CoA ester is a step in a recycling pathway that results in its epimerization to the?D?enantiomer, which is the only substrate whose oxygenation results in light emission.
