The catalase enzyme is inside almost all living cells. It protects cells from oxidative damage by breaking down hydrogen peroxide, which is generated during cell metabolism. People who have mutations in the gene for catalase have a metabolic disorder, which often causes oral sores. Because of its protective function, human catalase helps prevent diseases and possibly some aging processes, while isolated animal and plant catalases are also useful in commercial cleaning operations and food processing.
Human Catalase Enzyme Activity
Catalase is an extremely hard-working enzyme. It deactivates millions of hydrogen peroxide molecules per second. It destroys hydrogen peroxide in two steps. In the first step, catalase breaks down hydrogen peroxide by removing and binding one oxygen atom and then releasing the rest of the hydrogen peroxide molecule as water. In the second step, catalase breaks down a second hydrogen peroxide molecule by releasing oxygen gas and water. The optimal pH for human catalase activity is pH 7.
Human Catalase Enzyme Structure
The catalase enzyme is made up of four identical protein subunits. The protein chains of the subunits interweave, forming a stable structure. A stable structure is needed because catalase has to deal with hydrogen peroxide, a reactive compound. Each subunit of catalase contains an iron atom, which binds the oxygen atom of hydrogen peroxide during its decomposition.
Subcellular Localization of Catalase
The catalase enzyme resides in a cellular compartment, called a peroxisome. A peroxisome is a small intracellular organelle surrounded by a single-layer membrane. The peroxisome helps to separate hydrogen peroxide and its damaging effects from the rest of the cell. In plant cells, the peroxisome also carries out photorespiration.
Catalases in different animals and plants come in various sizes and shapes. Although many of these catalases also use an iron or heme group in their active center, some use manganese ions. Non-human catalases also play protective roles in cells. Commercial processes that use hydrogen peroxide use catalase enzymes to quench excess or left-over hydrogen peroxide.
Role of Catalase in Diabetes
Genetic deficiency of the catalase enzyme may increase the risk of type 2 diabetes, according to a 2008 report in the journal "Diabetes Care." Exposure to long-term intracellular hydrogen peroxide can damage the insulin-producing pancreatic beta cells. The study found low catalase activity in pregnant women with gestational diabetes, however, no ill effects occurred in these pregnancies. Although catalase plays an important role in combating oxidative cell damage, other enzymes also help to decompose harmful oxygen-containing compounds.
Catalse Deficiency Causes Gray Hair
Cells, called melanocytes, within hair follicles give hair its color. Hair is continually renewed and new melanocytes are produced from stem cell melanocytes during hair formation. As people age, hydrogen peroxide builds up in the hair follicle and hair shaft and the concentration of catalase gradually decreases. The result is bleaching of hairs, starting at the follicle.
- Protein Data Bank (PDB): Catalase
- Worthington Biochemical Corporation: Catalase
- Protein Knowledgebase: Catalase
- Clinical Chemistry: Blood Catalase Activity in Gestational Diabetes is Decreased but Not Associated with Pregnancy Complications
- The Faseb Journal: Senile Hair Graying: H2O2-mediated Oxidative Stress Affects Human Hair Color by Blunting Methionine Sulfoxide Repair
- Diabetes Care: Catalase Deficiency and Type 2 Diabetes
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