What is glucose oxidase?
Glucose oxidase is an FAD-dependent enzyme that links glucose oxidation with oxygen consumption and peroxide formation. These coupled changes underpin analytical and food-processing applications.
Glucose oxidase consumes oxygen and oxidises glucose. Glucose isomerase instead interconverts glucose and fructose.
The key idea
Oxygen, peroxide and pH are coupled process variables in glucose oxidation.
[3]
Core properties and EC classification
An EC number classifies a catalysed reaction. It does not specify a production strain, amino-acid sequence, preparation purity or operating optimum. Related proteins can perform the same classified reaction, while a commercial activity name may cover several reactions.
· Classification · Accepted activity · Reaction scope
· EC 1.1.3.4 · glucose oxidase · β- D -glucose + O 2 = D -glucono-1,5-lactone + H 2 O 2
· Substrate / system · Chemical distinction · Practical interpretation
· Glucose oxidation · Consumes glucose and oxygen · Produces a lactone and peroxide
· Lactone hydrolysis · Subsequent aqueous reaction · Contributes gluconic acid
· Catalase coupling · Removes peroxide · Returns part of the oxygen through a separate reaction
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Molecular weight: monomer, dimer or multimer?
A monomer contains one protein subunit; a homodimer contains two copies of the same subunit, and a higher oligomer contains more. A protein domain is a region within a chain, not an additional subunit. Likewise, mixing enzymes in a bottle does not establish that they form a stable molecular complex.
· Property of the named example · Evidence and interpretation
· Molecular weight of the example · Approximately 63.3 kDa for the deposited protein entity (one polypeptide; PDB 1CF3). This is not whole-formulation mass or a measured glycosylated mass.
· Monomer, dimer or multimer? · Monomer, as annotated for PDB 1CF3 biological assembly 1. UniProt P13006 describes the protein as: Homodimer.
· Model and experimental resolution · PDB 1CF3; 1.9 Å X-ray diffraction; representative chain A.
· Deposited protein sequence · 583 residues in the experimental entity; unresolved coordinates and biological processing are separate considerations.
The mass above is the deposited polypeptide-entity value. Glycosylation, precursor processing, linkers or omitted domains can change the experimentally observed mass. SDS–PAGE primarily informs denatured subunit size; native assembly needs evidence such as SEC–MALS, analytical ultracentrifugation or an appropriate structural analysis. The viewer shows one selected chain for clarity, not necessarily the complete biological assembly.
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FROM MOLECULE TO APPLICATIONOxygen, peroxide and pH are coupled process variables in glucose oxidation.
Natural sources and fermentation hosts
Aspergillus niger and Penicillium species are established sources. Fungal glucose oxidases are glycoproteins, so mature apparent mass differs from peptide-chain mass. The familiar fungal enzyme is generally homodimeric, although a deposited crystallographic assembly may contain only one chain.
Fungal fermentation, particularly Aspergillus systems, is established; recombinant routes also exist. FAD occupancy, glycosylation and stabilisers influence performance.
· Term · What it means in this report
· Natural donor of the model · Aspergillus niger — the organism associated with the displayed protein sequence.
· Expression host of the structural sample · Not separately specified in this structural record; do not infer a recombinant host.
· Manufacturing route · Fungal fermentation, particularly Aspergillus systems, is established; recombinant routes also exist. FAD occupancy, glycosylation and stabilisers influence performance.
· Supplied product · Use the linked product documentation for the actual grade, activity assay and declared source. A structural example does not establish the manufacturing organism or purity of the supplied preparation.
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Reaction mechanism and structure–function relationships
Glucose reduces enzyme-bound FAD; oxygen reoxidises the flavin, forming peroxide. The lactone subsequently hydrolyses to gluconic acid, which can alter pH. Oxygen limitation can constrain conversion even at high enzyme loading. Catalase can remove peroxide in coupled systems, but changes the oxygen balance.
THE REACTION, STEP BY STEP
1
Glucose reduces the bound FAD cofactor
2
Oxygen reoxidises FAD and peroxide forms
3
The lactone hydrolyses, producing gluconic acid
β-D-glucose + O₂→Glucono-1,5-lactone + H₂O₂
Conceptual reaction pathway; the stages describe function rather than atomic geometry.
From active-site chemistry to a useful process
Oxygen, peroxide and pH are coupled process variables in glucose oxidation. Measure glucose, dissolved oxygen and pH in parallel where feasible. Keep mixing and gas transfer comparable. If catalase is included, specify its activity separately because it changes peroxide accumulation and oxygen recycling.
The catalytic mechanism explains which chemical transformation is possible. It does not, by itself, establish the rate in a complex material. Substrate presentation, reaction-medium composition and retention of the active fold determine whether that chemistry can proceed usefully under the chosen conditions. This is why a defined-substrate activity measurement and an application trial provide complementary evidence.
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Discovery and scientific milestones
Discovery, purification, structural characterisation and industrial adoption are different historical milestones. The named studies below identify specific contributions; a publication date is not automatically the first discovery of every activity covered by the enzyme name.
1945
Biochemical and historical context
Coulthard and colleagues characterised notatin in 1945. Keilin and Hartree subsequently studied its glucose-oxidase properties and specificity, connecting the antibacterial preparation with defined enzyme chemistry.
[3]1999
Wohlfahrt and colleagues: molecular characterisation
The primary study associated with PDB 1CF3 is “1.8 and 1.9 A resolution structures of the Penicillium amagasakiense and Aspergillus niger glucose oxidases as a basis for modelling substrate complexes.”. The experimental structure links the named protein to a concrete molecular model, allowing its fold, substrate-binding region and assembly to be examined rather than inferred from the general enzyme name.
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Major industrial applications and research uses
Glucose assays and biosensors use optical or electrochemical coupling. Baking exploits controlled oxidative effects. Oxygen-removal applications require available glucose and management of peroxide generation.
01
Glucose analysis
Couple glucose oxidation to a measurable signal.
Measure success: Validate oxygen supply and matrix interference.
02
Baking
Use controlled oxidative effects.
Measure success: Assess dough performance rather than peroxide alone.
03
Oxygen management
Consume available oxygen where glucose is present.
Measure success: Track peroxide and pH as well as oxygen.
A research use, a development-stage process and an established commercial application do not imply the same level of readiness. Match the preparation to the target matrix and required grade, then validate the specific outcome described above. The product links below provide the route from this scientific overview to a defined supplied formulation.
Activity assays and interpreting experimental results
Peroxidase-coupled assays follow peroxide; oxygen electrodes follow oxygen consumption. Control glucose-anomer equilibration, oxygen supply and interfering reductants. State the measured endpoint and its calibration.
A useful experiment for this enzyme
Measure glucose, dissolved oxygen and pH in parallel where feasible. Keep mixing and gas transfer comparable. If catalase is included, specify its activity separately because it changes peroxide accumulation and oxygen recycling.
· Experimental question · Evidence to collect
· Is the enzyme active? · Measure an initial rate with a defined substrate, blank correction and a stated activity-unit definition.
· Does it work on this material? · Validate oxygen supply and matrix interference.
· Is the preparation stable? · Measure residual activity after a specified exposure, separately from activity during the exposure.
· Is the product what you intended? · Assess dough performance rather than peroxide alone.
Keep enzyme loading, substrate amount, mixing, temperature and sampling time explicit. Use a no-enzyme control to capture non-enzymatic changes and a suitable analytical blank for colour, background sugars, peptides or other interfering components. A time course is more informative than one endpoint when the reaction slows, because substrate depletion, loss of activity and product effects can produce similar plateaus.
Reading kinetic and operating data
Compare reported pH and temperature optima only when substrate and assay duration are comparable. An optimum describes the measured rate within an experiment; it is not a guarantee of long-incubation stability. For heterogeneous substrates, changes in accessibility can also affect apparent kinetic behaviour. Cite the protein, substrate and conditions alongside any kinetic constant rather than treating it as a universal property of the enzyme name.
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Common questions
Why can a glucose-rich reaction slow down?
Oxygen availability, product effects or enzyme loss may limit the rate.
Does catalase simply reverse glucose oxidation?
No. It decomposes peroxide without converting gluconic acid back to glucose.
Why can pH fall?
The lactone hydrolysis product is gluconic acid.
Continue exploring
Glucose Oxidase: Managing Oxygen, Glucose and Peroxide ↗Laccase deep dive ↗Catalase deep dive ↗
