Luciferase

Luciferase is a generic name for calcium ions (an analog of muscle contraction)^[1]. The reaction takes place in two steps:

The reaction is very energy efficient: nearly all of the energy input into the reaction is transformed into light. As a comparison, the incandescent light bulb loses about 90% of its energy to heat.

Luciferin and luciferase are not specific molecules. They are generic terms for a substrate and its associated catalyze a light-producing reaction. A variety of organisms regulate their light production using different luciferases in a variety of light-emitting reactions. The most famous are the fireflies, although the enzyme exists in organisms as different as the Jack-O-Lantern mushroom (Omphalotus olearius) and many marine creatures. In fireflies, the oxygen required is supplied through a tube in the abdomen called the abdominal trachea. Some organisms, notably certain click beetles, have several different luciferase enzymes, which each can produce different colors from the same luciferin. The luciferases of fireflies - of which there are over 2000 species - and of the Elateroidea (fireflies, click beetles and relatives) in general - are diverse enough to be useful in molecular phylogeny. The most thoroughly studied luciferase is that of the Photinini firefly Photinus pyralis.

Applications

Luciferase can be produced in the lab through genetic engineering for a number of purposes. Luciferase genes can be synthesized and inserted into organisms or transfected into cells. Mice, silkworms, and potatoes are just a few organisms that have already been engineered to produce the protein.

Ex-vivo imaging is a very powerful technique for studying cell populations in whole animals. Different types of cells (e.g. bone marrow stem cells, T-cells) can be engineered to express a luciferase allowing their non-invasive visualization inside a live animal using a sensitive CCD camera.

Light is emitted when luciferase is exposed to the appropriate luciferin heat shock proteins. The opportunities for using luciferase continue to expand.

See also

• Firefly
• Quorum sensing
• Bioluminescence

References

1. ^ IUBMB Enzyme Nomenclature Renilla luciferin reaction is triggered by calcium ions. (cited September 6, 2006)

• Thomas O Baldwin. Firefly luciferase: the structure is known, but the mystery remains Structure. 1996 Mar 15;4(3):223-8.
• Greer LF 3rd, Szalay AA. Imaging of light emission from the expression of luciferases in living cells and organisms: a review Luminescence. 2002 Jan-Feb;17(1):43-74.