Firefly luciferase is a bifunctional enzyme: ATP-dependent monooxygenase and a long chain fatty acyl-CoA synthetase

Firefly luciferase can catalyze the formation of fatty acyl-CoA via fatty acyl-adenylate from fatty acid in the presence of ATP, Mg²⁺ and coenzyme A (CoA). A long chain fatty acyl-CoA (C₁₆–C₂₀), produced by luciferase from a North American firefly (Photinus pyralis) and a Japanese firefly (Luciola cruciata), was isolated and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis. Of a number of substrates tested, linolenic acid (C_18:3) and arachidonic acid (C_20:4) appear to be suitable for acyl-CoA synthesis. This evidence suggests that firefly luciferase within peroxisomes of the cells in the photogenic organ may be a bifunctional enzyme, catalyzing not only the bioluminescence reaction but also the fatty acyl-CoA synthetic reaction.