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Bioluminescence:
Origins, Functions, Mechanisms and Applications
Hastings, J. Woodland1
Harvard University1
Abstract-
There are ~30 different extant bioluminescent systems (many more are
probably extinct), most being unrelated evolutionarily. The identities
and origins of the different luciferases and luciferins continue to
command attention. Homologies for three luciferases are now established,
and it is clear that they did not evolve from oxidases or oxygenases.
Two of these luciferases possess enzymatic properties similar to their
precursors: beetle luciferase and its acyl-CoA synthetase precursor
both catalyze adenylation, while aequorin and calmodulin both bind calcium.
The third, Renilla luciferase, has been found to have significant
similarities to the haloalkane dehalogenases, thus a completely different
type of reaction, mechanistically speaking. The relatively rare ability
to emit light leads to many different, sometimes exotic, uses. Indeed,
bioluminescence may be thought of as not being essential for life but
as a bag of tricks: the light can be used in diverse ways and for different
functions. Most of the perceived functions may be classed under three
main rubrics: defense, offense and communication. Biochemically, the
reaction involves the oxidation by molecular oxygen of a luciferin by
a luciferase with the formation of a peroxy intermediate, whose breakdown
provides the energy to give an electronically excited state, which then
emits a photon. It does not come from or depend on light absorbed, as
in fluorescence. And, it should be noted, the energy released in such
reactions is about 10 times greater than is obtained from the hydrolysis
of ATP. Practical applications have become increasingly important. Bioluminescence
offers unique features: it is self reporting and non intrusive, and
extremely sensitive; it can supplant the use of radioactivity. It provides
a powerful method for analytical determinations of many substances;
even more extensive are the reporter applications for monitoring gene
expression, using different luciferases and green fluorescent protein
(GFP), an antenna protein in coelenterate luminescence.
Keywords: luciferin/luciferase,
reporter genes, bioluminescence, peroxy enzyme intermediates
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