Biochemistry · Enzyme
Catalase !
Catalase breaks hydrogen peroxide down into water and oxygen; it works mainly in peroxisomes and in red blood cells.
Updated 2026-11-01
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Key facts
- 2 H₂O₂ → 2 H₂O + O₂, with a heme (iron) in the active site.
- It lives in peroxisomes, where β-oxidation of very-long-chain fatty acids produces H₂O₂.
- It is a tetramer; each subunit has a heme and binds NADPH, which protects it from inactivation.
- It works best when H₂O₂ is high; at low levels, glutathione peroxidase is more efficient.
Regulation
- Its expression rises with oxidative stress.
- Bound NADPH prevents excess H₂O₂ from inactivating it.
Inhibitors and toxins
- 3-Amino-1,2,4-triazole (aminotriazole)
- Cyanide and azide (bind the heme)
Clinical notes
- Acatalasemia (CAT variants) usually causes no symptoms; some people have mouth ulcers.
- Catalase-positive microbes (Staphylococcus, Aspergillus, Candida, Nocardia) mainly harm patients with chronic granulomatous disease.
- The catalase test with hydrogen peroxide separates staphylococci (they bubble) from streptococci in the laboratory.
Related
- Superoxide dismutase (SOD)
- Glutathione peroxidase (GPX)
- Reactive oxygen species and antioxidants
- Hemoglobin and 2,3-BPG
Test yourself
Think of the answer, then tap the question to see it.
What reaction does catalase catalyse?
It breaks 2 H₂O₂ into 2 H₂O and O₂ using a heme in the active site.
In which organelle is catalase abundant?
The peroxisome, where β-oxidation of very-long-chain fatty acids makes H₂O₂.
Why do catalase-positive microbes affect people with chronic granulomatous disease?
Their phagocytes make no superoxide and rely on microbial H₂O₂; catalase-positive microbes destroy it and survive.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: CAT: Catalase (human) (UniProt, 2026); CAT gene: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Acatalasemia: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); 1DGH: HUMAN ERYTHROCYTE CATALASE 3-AMINO-1,2,4-TRIAZOLE COMPLEX (RCSB Protein Data Bank, 2026).
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