Glucose oxidase
Encyclopedia
The glucose oxidase enzyme (GOx) is an oxido-reductase
that catalyses the oxidation of glucose
to hydrogen peroxide
and D-glucono-δ-lactone
. In cells, it aids in breaking the sugar down into its metabolite
s.
Glucose oxidase is widely used for the determination of free glucose in body fluids (diagnostics), in vegetal raw material, and in the food industry. It also has many applications in biotechnologies
, typically enzyme assays for biochemistry
including biosensors in nanotechnologies. It is often extracted from Aspergillus
niger
.
ic protein, the 3D structure of which has been elucidated.
The active site where glucose binds is in a deep pocket. The enzyme, like many proteins that act outside of cells, is covered with carbohydrate
chains.
) and does not act on α-D-glucose. But it is able to act on glucose, because in solution, the glucose is under cyclic form (at pH7, 63.6% of β-D-glucose and 36.4% of α-D-glucose, the linear form being negligible) and the oxidation displaces the equilibrium to β-D-glucose.
GOx catalyzes the oxidation of β-D-glucose into D-glucono-1,5-lactone
, which then hydrolyze
s to gluconic acid
.
In order to work as a catalyst, GOx requires a cofactor
, flavin adenine dinucleotide
(FAD). FAD is a common component in biological oxidation-reduction (redox reaction
s). Redox reactions involve a gain or loss of electrons from a molecule. In the GOx-catalyzed redox reaction, FAD works as the initial electron acceptor and is reduced to FADH2. Then FADH2 is oxidized by the final electron acceptor, molecular oxygen
(O2), which can do so because it has a higher reduction potential. O2 is then reduced to hydrogen peroxide
(H2O2).
reaction that vizualizes colorimetrically the formed H2O2, for the determination of free glucose in sera
or blood plasma
for diagnostics, using spectrometric assays manually or with automated procedures, and even point of use rapid assays.
Similar assays allows to monitor glucose levels in fermentation, bioreactors, and to control glucose in vegetal raw material and food products.
Enzyme electrode biosensor
s detect levels of glucose by keeping track of the number of electron
s passed through the enzyme
by connecting it to an electrode
and measuring the resulting charge. This has a possible application in the world of nanotechnology
when used in conjunction with tiny electrodes as glucose sensors for diabetic
s.
In manufacturing, GOx is used as an additive thanks to its oxidising effects: it prompts for stronger dough in bakery
, replacing oxidants such as bromate. It also helps remove oxygen from food packaging, or D-glucose from egg white to prevent browning.
Glucose oxidase is found in honey and acts as a natural preservative. GOx at the surface of the honey reduces atmospheric O2 to hydrogen peroxide
(H2O2), which acts as an antimicrobial
barrier. GOx similarly acts as a bactericide in many cells (fungi, immune cells).
. Notatin was shown to be identical to Penicillin B and glucose oxidase, enzymes extracted from other molds besides P. notatum; it is now generally known as glucose oxidase.
Early experiments showed that notatin exhibits in vitro antibacterial activity (in the presence of glucose) due to hydrogen peroxide formation. In vivo tests showed that notatin was not effective in protecting rodents from Streptococcus haemolyticus, Staphylococcus aureus
, or salmonella
, and caused severe tissue damage at some doses.
Oxidoreductase
In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule to another...
that catalyses the oxidation of glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
to hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
and D-glucono-δ-lactone
Glucono delta-lactone
Glucono delta-lactone is a naturally-occurring food additive with the E number E575 used as a sequestrant, an acidifier, or a curing, pickling, or leavening agent. It is a lactone of D-gluconic acid. Pure GDL is a white odorless crystalline powder.GDL is commonly found in honey, fruit juices,...
. In cells, it aids in breaking the sugar down into its metabolite
Metabolite
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...
s.
Glucose oxidase is widely used for the determination of free glucose in body fluids (diagnostics), in vegetal raw material, and in the food industry. It also has many applications in biotechnologies
Biotechnology
Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...
, typically enzyme assays for biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...
including biosensors in nanotechnologies. It is often extracted from Aspergillus
Aspergillus
Aspergillus is a genus consisting of several hundred mold species found in various climates worldwide. Aspergillus was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli...
niger
Aspergillus niger
Aspergillus niger is a fungus and one of the most common species of the genus Aspergillus. It causes a disease called black mold on certain fruits and vegetables such as grapes, onions, and peanuts, and is a common contaminant of food...
.
Structure
GOx is a dimerProtein dimer
In biochemistry, a dimer is a macromolecular complex formed by two, usually non-covalently bound, macromolecules like proteins or nucleic acids...
ic protein, the 3D structure of which has been elucidated.
The active site where glucose binds is in a deep pocket. The enzyme, like many proteins that act outside of cells, is covered with carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
chains.
Activity
The glucose oxidase binds specifically to β-D-glucopyranose (a hemiacetal form of the six-carbon sugar glucoseGlucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
) and does not act on α-D-glucose. But it is able to act on glucose, because in solution, the glucose is under cyclic form (at pH7, 63.6% of β-D-glucose and 36.4% of α-D-glucose, the linear form being negligible) and the oxidation displaces the equilibrium to β-D-glucose.
GOx catalyzes the oxidation of β-D-glucose into D-glucono-1,5-lactone
Glucono delta-lactone
Glucono delta-lactone is a naturally-occurring food additive with the E number E575 used as a sequestrant, an acidifier, or a curing, pickling, or leavening agent. It is a lactone of D-gluconic acid. Pure GDL is a white odorless crystalline powder.GDL is commonly found in honey, fruit juices,...
, which then hydrolyze
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
s to gluconic acid
Gluconic acid
Gluconic acid is an organic compound with molecular formula C6H12O7 and condensed structural formula HOCH24COOH. It is one of the 16 stereoisomers of 2,3,4,5,6-pentahydroxyhexanoic acid....
.
In order to work as a catalyst, GOx requires a cofactor
Cofactor (biochemistry)
A cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity. These proteins are commonly enzymes, and cofactors can be considered "helper molecules" that assist in biochemical transformations....
, flavin adenine dinucleotide
FAD
In biochemistry, flavin adenine dinucleotide is a redox cofactor involved in several important reactions in metabolism. FAD can exist in two different redox states, which it converts between by accepting or donating electrons. The molecule consists of a riboflavin moiety bound to the phosphate...
(FAD). FAD is a common component in biological oxidation-reduction (redox reaction
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
s). Redox reactions involve a gain or loss of electrons from a molecule. In the GOx-catalyzed redox reaction, FAD works as the initial electron acceptor and is reduced to FADH2. Then FADH2 is oxidized by the final electron acceptor, molecular oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
(O2), which can do so because it has a higher reduction potential. O2 is then reduced to hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
(H2O2).
Applications
Glucose oxidase is widely used, coupled to peroxidasePeroxidase
Peroxidases are a large family of enzymes that typically catalyze a reaction of the form:For many of these enzymes the optimal substrate is hydrogen peroxide, but others are more active with organic hydroperoxides such as lipid peroxides...
reaction that vizualizes colorimetrically the formed H2O2, for the determination of free glucose in sera
Sera
Sera may refer to:- Music :* Sera, a Symphonic rock/electronica singer/composer/producer* Sera, the well known bass player in Greece- Places :* Sera, Hiroshima, a town in Japan* Sera District, Hiroshima, a district located in Hiroshima, Japan...
or blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
for diagnostics, using spectrometric assays manually or with automated procedures, and even point of use rapid assays.
Similar assays allows to monitor glucose levels in fermentation, bioreactors, and to control glucose in vegetal raw material and food products.
Enzyme electrode biosensor
Biosensor
A biosensor is an analytical device for the detection of an analyte that combines a biological component with a physicochemical detector component.It consists of 3 parts:* the sensitive biological element A biosensor is an analytical device for the detection of an analyte that combines a biological...
s detect levels of glucose by keeping track of the number of electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s passed through the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
by connecting it to an electrode
Electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...
and measuring the resulting charge. This has a possible application in the world of nanotechnology
Nanotechnology
Nanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometres...
when used in conjunction with tiny electrodes as glucose sensors for diabetic
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
s.
In manufacturing, GOx is used as an additive thanks to its oxidising effects: it prompts for stronger dough in bakery
Bakery
A bakery is an establishment which produces and sells flour-based food baked in an oven such as bread, cakes, pastries and pies. Some retail bakeries are also cafés, serving coffee and tea to customers who wish to consume the baked goods on the premises.-See also:*Baker*Cake...
, replacing oxidants such as bromate. It also helps remove oxygen from food packaging, or D-glucose from egg white to prevent browning.
Glucose oxidase is found in honey and acts as a natural preservative. GOx at the surface of the honey reduces atmospheric O2 to hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
(H2O2), which acts as an antimicrobial
Antimicrobial
An anti-microbial is a substance that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans. Antimicrobial drugs either kill microbes or prevent the growth of microbes...
barrier. GOx similarly acts as a bactericide in many cells (fungi, immune cells).
Related enzymes: Notatin and other names
Notatin, extracted from antibacterial cultures of Penicillium notatum, was originally named Penicillin A, but was renamed to avoid confusion with penicillinPenicillin
Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....
. Notatin was shown to be identical to Penicillin B and glucose oxidase, enzymes extracted from other molds besides P. notatum; it is now generally known as glucose oxidase.
Early experiments showed that notatin exhibits in vitro antibacterial activity (in the presence of glucose) due to hydrogen peroxide formation. In vivo tests showed that notatin was not effective in protecting rodents from Streptococcus haemolyticus, Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...
, or salmonella
Salmonella
Salmonella is a genus of rod-shaped, Gram-negative, non-spore-forming, predominantly motile enterobacteria with diameters around 0.7 to 1.5 µm, lengths from 2 to 5 µm, and flagella which grade in all directions . They are chemoorganotrophs, obtaining their energy from oxidation and reduction...
, and caused severe tissue damage at some doses.
External links
- "Glucose Oxidase: A much used and much loved enzyme in biosensors" at University of PaisleyUniversity of PaisleyThe University of the West of Scotland is a university operating from four campuses in south-western Scotland, in the towns of Paisley, Hamilton, Ayr and Dumfries. The present institution dates from August 2007, following the merger of the University of Paisley with Bell College, Hamilton...