Luciferase

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Luciferase is a generic name for enzymes commonly used in nature for bioluminescence. The name itself is derived from Lucifer, which means light-bearer. The most famous one is firefly luciferase (Template:EC number) from the firefly Photinus pyralis. In luminescent reactions, light is produced by the oxidation of a luciferin (a pigment), sometimes involving Adenosine triphosphate (ATP). The rates of this reaction between luciferin and oxygen are extremely slow until they are catalyzed by luciferase, often mediated by the presence of calcium ions (an analog of muscle contraction). The reaction takes place in two steps:

luciferin + ATP → luciferyl adenylate + PP_i

luciferyl adenylate + O₂ → oxyluciferin + AMP + light

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. Image:Luciferase-1BA3.png Luciferin and luciferase do not refer to a particular molecule. They are generic terms for a substrate and its associated enzyme (or protein) that catalyze a light-producing reaction. A variety of species regulate their light production using a luciferase. The most famous is the firefly, although it even exists in organisms as different as the Jack-O-Lantern mushroom and many marine creatures. In the firefly, the oxygen required is supplied through a tube in the abdomen called the abdominal trachea. Some organisms, notably the click beetles, have several different luciferase enzymes, which each can produce different colors from the same luciferin.

Luciferase can be produced in the lab through genetic techniques, and has a number of uses. Genes for luciferase can be genetically engineered into organisms or transfected into cells. Mice, silkworms, and potatoes are just a few organisms that have already been engineered to produce the protein.

Light will be emitted when the luciferase is exposed to the right luciferin substrate. Photon emission can be detected by light sensitive apparatus such as a luminometer or specific microscopes. This allows visualization of certain biological processes, stages of infection, and provides other valuable sources of information. Luciferase can be used in blood banks to determine if red blood cells are starting to break down. Laboratories can use luciferase to produce light in the presence of certain diseases. Luciferase is used as a reporter protein in molecular studies, for example to test the activity of transcription from specific promoters in with luciferase transfected cells, or to detect the level of cellular ATP. Luciferase is a very heat labile protein that is used in studies on protein denaturation, testing for example the protective capacities of heat shock proteins. The possibilities for uses for luciferase continue to expand.