The secreted luciferases responsible for light emission of marine copepods have gained popularity for being used in noninvasive imaging of intracellular events. The secreted luciferase of copepod Gaussia princeps is a one-subunit protein catalyzing

Proteins engineered to generate fluorescent or bioluminescent signals are commonly used for the non-invasive study of a variety of biological processes and diseases in animals and humans (1-3). Usually the enhanced green fluorescent proteins, the variant

Gaussia princeps luciferase (GLuc) generates an intense burst of blue light when exposed to coelenterazine in the absence of ATP. Here we show that this 5‐disulfide containing enzyme can be used as a facile and convenient substrate for studies of