Which group of chemicals is responsible for the yellow light emission from many firefly species?

Luciferase is the name of a group of oxidative enzymes responsible for characteristic yellow light emission from several firefly species. These chemicals are useful for scientific research, food safety testing and also forensic tests. At a time when luciferase was first discovered, fireflies were the only source of it.  Now a days, synthetic lucifease is available but still many companies harvest fireflies for them.