Luciferase enzymes

Although most anesthetics are achiral or are adininistered as racemic mixture, the anesthetic actions are stereoselective. This property can define a specific, rather than a nonspecific, site of action. Stereoselectivity is observed for such barbiturates as thiopental, pentobarbital, and secobarbital. The (3)-enantiomer is modestly more potent (56,57). Additionally, the volatile anesthetic isoflurane also shows stereoselectivity. The (3)-enantiomer is the more active (58). Further evidence that proteins might serve as appropriate targets for general anesthetics come from observations that anesthetics inhibit the activity of the enzyme luciferase. The potencies parallel the anesthetic activities closely (59,60). 

The membrane enzyme luciferase, responsible for light emission in fireflies, is sensitive to anesthetics (20,21), and the concentrations of inhalational agents which inhibit luciferase are the same as those which cause general anesthesia. Studies of various classes of inhalational agents and luciferase demonstrated that above a certain chain length in a homologous series, a point is reached where higher members are not anesthetic. The same cut-off effect in efficacy is observed in anesthesia (22). This effect is not explainable by Hpid theory. 

The role of a cationic surfactant must be to provide a necessary hydrophobic and polarized environment for the molecule of luciferin for its luminescence reaction. In the case of a common luciferin-luciferase reaction, such an environment is provided by the enzyme luciferase. The chemical structures of PMs, as well as that of the natural luciferin, have not been determined yet (see the next section). 

In chemiluminescence immunoassay the antigen is tagged with a molecule such as luminol or an acridinium ester which emits light with a high quantum yield on oxidation. Alternatively, the antigen may be labelled with a bio-luminescent molecule such as luciferin, which emits light when oxidized by the enzyme luciferase. 

With isotopes it has been possible to show that all enzyme-catalyzed reactions are stereospecific. Before the availability of isotopes, there was no way of testing this generalization. Of course there are some apparent exceptions to prove the rule. Bently has listed a considerable number (2>, Table XIII, Chapter 6). The most interesting one to me seems to be luciferase, but that is an exception that isn t an exception. Thus, the enzyme luciferase acts on its substrate luciferin (2), in the presence of ATP and O2, to oxidize the luciferin to oxyluciferin (3). The reaction consists of an initial activation of the substrate by ATP to give luciferyl adenylate, after which the oxidation takes place. When the natural enantiomer (synthesized from D-cysteine) is activated and oxidized, light is emitted. The other enantiomer is also acted on by the enzyme, and is converted to the adenylate, but oxyluciferin is not formed, and there is no bioluminescence 37,38,38a)... 

For example, the enzyme luciferase is inhibited by clinically effective concentrations of anaesthetics (Franks and Lieb, 1984). 

FIGURE 3-1 Some functions of proteins, (a) The light produced by fireflies is the result of a reaction involving the protein luciferin and ATP, catalyzed by the enzyme luciferase (see Box 13-2). (b) Erythrocytes contain large amounts of the oxygen-transporting protein hemoglobin. (c) The protein keratin, formed by all vertebrates, is the chief structural component of hair, scales, horn, wool, nails, and feath-... 

Figure 5.26 Mechanism of a bioluminescence reaction. A luciferin is oxidized in the presence of an enzyme (luciferase Lz) and adenosine triphosphate, ATP...

Three chemicals must be present in order for bioluminescence to occur oxygen, luciferin, and the enzyme luciferase. The type of luciferin present is different in different animals. Because enzymes are specific to the chemicals they bind with, the luciferase is also... 

Dr. Abdullah Kirumira, President and lead scientist at BioMedica Diagnostics in Windsor, Nova Scotia, has developed a way to speed up drug testing. This method uses compressed carbon dioxide and a dry chemistry diagnostics system including the firefly enzyme, luciferase. 

To learn more about the biotech applications of using the firefly enzyme, luciferase, you can go to BioMedica s web site. 

Luminescence (or chemiluminescence) is another phenomenon in which light is emitted, but here the energy for the initial excitation of electrons is provided by a chemical reaction rather than by electromagnetic radiation. An example is the action of the enzyme luciferase, extracted from fireflies, which catalyses the following reaction ... 

One widely used enzyme mediated chemiluminescence immunoassay uses the firefly enzyme luciferase that catalyzes the oxidation of o-Luciferin in the presence of ATP. o-luciferin, but not luciferin esters such as phosphates, is oxidized in the presence... 

The reporter gene is the luc operon from the firefly Photinus pyralis. This operon codes for an enzyme, luciferase, that catalyses the reaction between D-luciferin (the substrate), and oxygen, and requires ATP as a cofactor. This reaction produces the emission light that provides the measure of enzyme activity. The oxidation of one molecule of luciferin involves one ATP molecule and releases one photon (a stoichiometric reaction) (DeLuca and McElroy, 1974 Wood el al. 1989). The reaction can be summarized as follows ... 

A familiar example of chemiluminescence is the light emitted by a firefly. In the firefly reaction, an enzyme, luciferase, catalyzes the oxidative phosphorylation reaction of luciferin with adenosine triphosphate to produce oxyluciferin, carbon dioxide, adenosine monophosphate, and light. Chemiluminescence involving a biological or enzyme reaction is often termed bioluminescence. The popular light stick is another familiar example of chemiluminescence. 

The firefly Photinus pyralis) is a familiar example of chemiluminescence. The photochemical reaction requires the enzyme luciferase (EC 1.13.12.7). In the presence of and the substrate luciferin, ATP is utilized in the following reaction... 

Chemiluminescence is also found in fireflies. The male firefly uses the reaction of a luciferin substrate and the enzyme luciferase with oxygen, with adenosine triphosphate (ATP) as an energy source, to create the illumination it uses to attract a mate. Because the detection of very minute amounts of light is possible, chemiluminescence and bioluminescence have become the basis of many sensitive analytical and bioanalytical techniques or assays used to quantify particular compounds in samples. Indeed, the use of these techniques is broad enough to justify the existence of a journal devoted to them, the Journal of Bioluminescence and Chemiluminescence. 

Luciferin. A generic term referring to a substrate which, upon oxidation by the enzyme luciferase, produces bioluminescence. Luciferins isolated from different species... 

Fireflies are one of several species that emit light as a result of a retro (i.e., reverse) [2 -I- 2] cycloaddition reaction, similar to the reaction that produces the cold light in light sticks (Section 29.4). Fireflies have an enzyme (luciferase) that catalyzes the reaction between luciferin, ATP, and molecular oxygen that forms a compound with an unstable four-membered ring. When the four-membered ring breaks, an electron in... 

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