has substrate has role has participant Luciferin 4-monooxygenase measured entity substrate coupled enzyme activity measurement method luciferin coupled enzyme activity measurement method The effect of a perturbagen on an enzyme activity is coupled to a secondary signal. The activity of an enzyme, e.g. luciferase is limited by the availability of one of its substrates, namely, luciferin, which is coupled to the activity of another enzyme, e.g. a Cytochrome P450, protease, etc. beetle luciferin