glucose oxidase

Several species of fungi and insects synthesize glucose oxidase, which produces hydrogen peroxide, which kills bacteria.

Notatin, extracted from antibacterial cultures of Penicillium notatum, was originally named Penicillin A, but was renamed to avoid confusion with penicillin.{{cite journal | vauthors = Coulthard CE, Michaelis R, Short WF, Sykes G | title = Notatin: an anti-bacterial glucose-aerodehydrogenase from Penicillium notatum Westling and Penicillium resticulosum sp. nov | journal = The Biochemical Journal | volume = 39 | issue = 1 | pages = 24–36 | year = 1945 | pmid = 16747849 | pmc = 1258144 | doi = 10.1042/bj0390024}} Notatin was shown to be identical to Penicillin B and glucose oxidase, enzymes extracted from other molds besides P. notatum;{{cite journal | vauthors = Keilin D, Hartree EF | title = Specificity of glucose oxidase (notatin) | journal = The Biochemical Journal | volume = 50 | issue = 3 | pages = 331–41 | date = Jan 1952 | pmid = 14915954 | pmc = 1197657 | doi = 10.1042/bj0500331}} 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.{{cite journal | vauthors = Broom WA, Coulthard CE, Gurd MR, Sharpe ME | title = Some pharmacological and chemotherapeutic properties of notatin | journal = British Journal of Pharmacology and Chemotherapy | volume = 1 | issue = 4 | pages = 225–233 | date = Dec 1946 | pmid = 19108091 | pmc = 1509745 | doi = 10.1111/j.1476-5381.1946.tb00041.x }} 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.

Glucose oxidase is also produced by the hypopharyngeal glands of honeybee workers and deposited into honey where it 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.{{cite journal | vauthors = Bucekova M, Valachova I, Kohutova L, Prochazka E, Klaudiny J, Majtan J | title = Honeybee glucose oxidase--its expression in honeybee workers and comparative analyses of its content and H₂O₂-mediated antibacterial activity in natural honeys | journal = Die Naturwissenschaften | volume = 101 | issue = 8 | date = Aug 2014 | pages = 661–670 | pmid = 24969731 | doi = 10.1007/s00114-014-1205-z | bibcode = 2014NW....101..661B | s2cid = 16338921 }}

File:Glucose oxidase enzyme from Aspergillus niger.png

GOx is a dimeric 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. GOx is a glucose oxidising enzyme with a molecular weight of 160 kDa. It is a dimeric glycoprotein consisting of two subunits each weighing 80 kDa. Flavinadenine dinucleotide (FAD) in the active site is buried approximately 1.5 nm inside the protein shell and acts as the initial electron acceptor.{{cite journal |last1=Mano |first1=Nicolas |title=Engineering glucose oxidase for bioelectrochemical applications. |journal=Bioelectrochemistry |date=2019 |volume=128 |pages=218–240}}

At pH 7, glucose exists in solution in cyclic hemiacetal form as 63.6% β-D-glucopyranose and 36.4% α-D-glucopyranose, the proportion of linear and furanose form being negligible. The glucose oxidase binds specifically to β-D-glucopyranose and does not act on α-D-glucose. It oxidises all of the glucose in solution because the equilibrium between the α and β anomers is driven towards the β side as it is consumed in the reaction.

Glucose oxidase catalyzes the oxidation of β-D-glucose into D-glucono-1,5-lactone, which then hydrolyzes into gluconic acid.

In order to work as a catalyst, GOx requires a coenzyme, flavin adenine dinucleotide (FAD). FAD is a common component in biological oxidation-reduction (redox) reactions. 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 FADH⁻.{{cite journal |last1=Sanner |first1=Christoph |display-authors=etal |title=15N‐ and 13C‐NMR investigations of glucose oxidase from Aspergillus niger |journal=European Journal of Biochemistry |date=March 1991 |volume=196 |issue=3 |pages=663–672 |doi=10.1111/j.1432-1033.1991.tb15863.x |pmid=2013289 |doi-access=free }} Then FADH⁻ 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).

Glucose oxidase is widely used coupled to peroxidase reaction that visualizes 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.{{cite journal |vauthors= Raba J, Mottola HA |title= Glucose Oxidase as an Analytical Reagent |journal= Critical Reviews in Analytical Chemistry |volume= 25 |issue= 1 |pages= 1–42 |year= 1995 |doi= 10.1080/10408349508050556 |url= http://www.biosensing.net/EBLA/Corso/Lezione%2001/GOD.PDF |access-date= 2009-01-08 |archive-date= 2021-01-10 |archive-url= https://web.archive.org/web/20210110064251/http://www.biosensing.net/EBLA/Corso/Lezione%2001/GOD.PDF |url-status= dead }}

Similar assays allows the monitoring of glucose levels in fermentation, bioreactors, and to control glucose in vegetal raw material and food products.{{Citation needed|date=August 2012}} In the glucose oxidase assay, the glucose is first oxidized, catalyzed by glucose oxidase, to produce gluconate and hydrogen peroxide. The hydrogen peroxide is then oxidatively coupled with a chromogen to produce a colored compound which may be measured spectroscopically. For example, hydrogen peroxide together with 4 amino-antipyrene (4-AAP) and phenol in the presence of peroxidase yield a red quinoeimine dye that can be measured at 505 nm. The absorbance at 505 nm is proportional to concentration of glucose in the sample.

Enzymatic glucose biosensors use an electrode instead of O₂ to take up the electrons needed to oxidize glucose and produce an electronic current in proportion to glucose concentration.{{cite journal |vauthors= Blanford CF |title= The birth of protein electrochemistry |journal= Chemical Communications |volume= 49 |issue= 95 |pages= 11130–11132 |date= Dec 2013 |pmid= 24153438 |doi= 10.1039/C3CC46060F |publisher= Royal Society of Chemistry}} This is the technology behind the disposable glucose sensor strips used by diabetics to monitor serum glucose levels.{{cite journal |vauthors= Cass AE, Davis G, Francis GD, Hill HA, Aston WJ, Higgins IJ, Plotkin EV, Scott LD, Turner AP |title= Ferrocene-mediated enzyme electrode for amperometric determination of glucose |journal= Analytical Chemistry |volume =56 |issue= 4 |pages= 667–671 |date= Apr 1984 |pmid= 6721151 |doi= 10.1021/ac00268a018 |publisher= American Chemical Society}}

In manufacturing, GOx is used as an additive thanks to its oxidizing effects: it prompts for stronger dough in baking, replacing oxidants such as bromate.{{cite journal |vauthors= Wong CM, Wong KH, Chen XD |title= Glucose oxidase: natural occurrence, function, properties and industrial applications |journal= Applied Microbiology and Biotechnology |volume= 78 |issue= 6 |pages= 927–38 |date= April 2008 |pmid= 18330562 |doi= 10.1007/s00253-008-1407-4|s2cid= 2246466 }} It is also used as a food preservative to help remove oxygen and glucose from food when packaged such as dry egg powder to prevent unwanted browning and undesired taste.{{cite journal |vauthors= Dubey MK, Zehra A, Aamir M, Meena M, Ahirwal L, Singh S, Shukla S, Upadhyay RS, Bueno-Mari R, Bajpai VK |display-authors= 6 |title= Improvement Strategies, Cost Effective Production, and Potential Applications of Fungal Glucose Oxidase (GOD): Current Updates |journal= Frontiers in Microbiology |volume= 8 |pages= 1032 |date= 2017 |pmid= 28659876 |pmc= 5468390 |doi= 10.3389/fmicb.2017.01032|doi-access= free }}

Wound care products, such as "Flaminal Hydro" make use of an alginate hydrogel containing glucose oxidase and other components as an oxidation agent.

A nasal spray from a bag-on-valve device that mixes glucose oxidase with glucose has undergone clinical trials in 2016 for the prevention and treatment of the common cold.{{ClinicalTrialsGov|NCT01883427|Nasal Spray With Glucose Oxidase Preventing Common Cold in Pre-school Children}}{{ClinicalTrialsGov|NCT01883440|Glucose Oxidase as Treatment Against Common Cold}}{{ClinicalTrialsGov|NCT01883453|A Nasal Spray With Glucose Oxidase as a Treatment of Common Cold}}

• Oxidoreductase
• Glucose meter

{{reflist|33em}}

• [https://web.archive.org/web/20040820162613/http://www-biol.paisley.ac.uk/marco/enzyme_electrode/chapter3/chapter3_page1.htm "Glucose Oxidase: A much used and much loved enzyme in biosensors"] at University of Paisley
• {{MeSH name|Glucose+Oxidase}}

{{Alcohol oxidoreductases}}

{{Enzymes}}

{{Portal bar|Biology|border=no}}

Category:EC 1.1.3