Luciferin-Luciferase Pathway скачать в хорошем качестве

Luciferin-Luciferase Pathway

Transcript: Bioluminescence is an organism’s ability to convert chemical energy into light, and it is one of the most fascinating naturally-occurring phenomena on earth [1]. Although bioluminescence is present in certain land animals, it is most common in organisms found in the ocean. This unique characteristic is used for survival either through offence, defence, reproduction, or communication [2]. One well known bioluminescent creature is the angler fish who you may recognize from ‘Finding Nemo’. Angler fish have a symbiotic relationship with photobacteria who live in their esca and can be used to attract prey in return for protection [3]. Alternatively, deep sea shrimp use their bioluminescence as a defence mechanism by repelling a blue secretion from their mouth to deter predators [4]. A more famous use of bioluminescence is seen in fireflies who attempt to find a mate using intricate light dances [5]. The use of bioluminescence for communication can be seen in firefly squid who can use their photophores to attract a mate or to warn other squid of potential danger [6]. The secret behind the rare ability that these organism exhibit lies in the luciferin-luciferase pathway. Luciferase is an oxidoreductase enzyme that acts on the luciferin substrate present in organisms. Luciferins differ in molecular structure from one organism to another and every luciferin has a complementary luciferase enzyme [7][8]. We will walk through a typical luciferase-catalyzed reaction using fireflies, as an example. This reaction takes place in the peroxisomes of photocyte cells where luciferase is found and occurs at an optimal pH of 7.5 to 7.8 and around 30 degrees Celsius [9][10]. The substrate present in this specific reaction is D-firefly luciferin and the enzyme is firefly luciferase [5]. At the luciferase active site, an adenylation between D-luciferin and ATP produces luciferyl-adenosine monophosphate and an inorganic pyrophosphate by-product [5]. Luciferyl-AMP is then oxidized by the addition of O2 [5]. Next AMP is removed and dioxethanone is created [5]. An excited oxyluciferin molecule is then produced from the loss of CO2 [5]. Finally, oxyluciferin transitions from its excited state to its ground state through the emission of a visible photon [5]. The sustainability of this reaction is maintained by the enzymatic regeneration of D-luciferin from ground state oxyluciferin [5]. The particular oxyluciferin molecule pictured here emits the photon at 568nm, which humans perceive as yellow on the visible light spectrum [11]. The colour of light produced during this reaction is dictated by the different luciferin molecule present which affects the final structure of the excited oxyluciferin [11]. Since organisms develop desired traits through evolution, the vitality of producing a certain colour would dictate the chemical composition of the luciferin molecule present in their body. The luciferase enzyme has proven to be an extremely useful tool in various biomedical applications. One of which is pyrosequencing, a technique for sequencing DNA where the addition of nucleotides in a strand of DNA is detected by the production of light [12]. When a certain dNTP binds to the DNA strand, an inorganic pyrophosphate is released and is converted to ATP [12]. This ATP is then used by luciferase to produce a flash of light whose intensity is proportional to the number of nucleotides added [12]. Using computers, the dNTP environment that DNA fragments are placed into is controlled, and the intensity of light produced from the reaction is recorded [12]. With this information, computers can successfully output the DNA sequence for scientists to study further. This is just one of many of the incredible applications of the luciferin-luciferase pathway. Can you think of other ways that this enzyme might be useful for future biomedical advancements? See reference in the comments.