concept

Luciferase

The enzyme that catalyzes the light reaction - it grabs the fuel molecule luciferin, joins it to oxygen, and steers the reaction so the product lands excited and then releases light. If luciferin is the candle, luciferase is the hand that strikes and steadies the flame. Each independent bioluminescent system on Earth uses a different, non-homologous luciferase - evidence that glow was reinvented many times. A special variant is the photoprotein (such as aequorin), which holds the reaction pre-loaded and flashes only when calcium ions arrive.