 Luciferase
Luciferase is a generic name for enzymes commonly used
in nature for bioluminescence. The most famous one is
firefly luciferase
(EC 1.13.12.7).
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 triggered
by the presence of luciferase. The reaction takes place in
two steps:
luciferin + ATP --> luciferyl adenylate + PPi
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.
Luciferin and luciferase do
not refer to a particular molecule. They are generic terms
for a light-producing chemical and
its associated regulatory compound, usually a protein. A
wide 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 wide variety of uses. Genes for luciferase can
be genetically engineered into organisms so that they glow
when exposed to the right luciferin. This allows visualization
of certain biological processes, stages of infection, and
provides other valuable sources of information. Mice, silkworms,
and potatoes are just a few organisms that have already been
engineered to produce the chemical. 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. The possibilities
for uses for luciferase continue to expand.
One peculiar application of luciferase was when a team of
students from the University of Hertfordshire made news with
their proposal to genetically engineer christmas trees to
glow without lights, using luciferase (in addition to other
bioluminescent chemicals). Luciferin would be added to a
fertilizer used for the tree, which would react with the
luciferase that the tree produces on its own.
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