Factors affecting the cellular expression of bacterial luciferase.

The in vivo expression of cellular bacterial luciferase has been defined as the luciferase expression quotient, measured as the ratio of the bioluminescence intensity in vivo to the in vitro activity of luciferase in crude cell extracts. The expression is greater in the presence of inhibitors of the electron transport system such as cyanide and N-heptyl-4-hydroxy-quinoline and also at lower oxygen tensions. The higher expression of the cellular luciferase under these conditions is postulated to be due to an increase in the intracellular levels of reduced coenzymes which enhance both the reduction of flavin and the reduction of fatty acid to aldehyde. Both FMNH2 and aldehyde are substrates in the light emitting reaction.