Catalase

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Catalase
Catalase
Ribbon model of human catalase according to PDB  1DGF

Existing structural data : 1dgb , 1f4j , 1qqw

Properties of human protein
Mass / length primary structure 526 amino acids
Secondary to quaternary structure Homotetramer
Cofactor Hamm
Identifier
Gene name CAT
External IDs
Enzyme classification
EC, category 1.11.1.6 ,  oxidoreductase
Substrate 2 H 2 O 2
Products O 2 + 2 H 2 O
Occurrence
Homology family Catalase
Parent taxon Creature

Catalase ( gene name: CAT ) is an enzyme that converts hydrogen peroxide (H 2 O 2 ) into oxygen (O 2 ) and water (H 2 O). Hydrogen peroxide results from the breakdown of hyperoxides by superoxide dismutase . It is a by-product of the breakdown of purines and the oxidation of fatty acids and can damage the genome and proteins . Catalases are therefore found in almost all aerobic living organisms, in humans especially in the peroxisomes of the liver and kidneys , and in the erythrocytes . Mutations in the CAT gene can lead to hereditary catalase deficiency ( akatalasia ), which is common in Japan .

Systematics

Catalases are divided into three classes based on sequence and structure .

  • monofunctional heme- containing enzymes
  • bifunctional heme-containing catalase peroxidases
  • manganese-containing enzymes (without heme group)

The human catalase ( PDB  1DGF ) consists of four identical subunits of 60 kDa each  . Each of these contains a heme group and a NADPH binding site.

Catalyzed reaction

The reaction takes place in two steps. In the first step, hydrogen peroxide is reduced and the enzyme is oxidized , creating the product water.

In the second step, both hydrogen peroxide and the enzyme are reduced and oxygen is oxidized and thus released as a product in addition to another water molecule.

The sum equation is:

Both the turnover number and the catalytic efficiency of the enzyme are among the highest values ​​ever found for enzymes ( table ).

At low hydrogen peroxide concentrations, the oxidized catalase can oxidize methanol and ethanol via the aldehyde to form acid .

Use in the laboratory

In microbiology, the catalase test is used to differentiate between bacteria. The differentiation of catalase-positive staphylococci from catalase-negative streptococci is of particular clinical importance. A drop of catalase reagent (3 percent hydrogen peroxide solution) is placed on a microscope slide and a loop of bacterial material is briefly held in it. Positive reaction: direct bubbling, blistering; Negative reaction: no or delayed effervescence. Alternatively, diluted hydrogen peroxide can be dripped directly onto a bacterial colony on an agar plate.

Most aerobic and facultative anaerobic bacteria as well as fungi have the enzyme catalase, which is able to break down the H 2 O 2 , which is toxic to the cells .

Hydrogen peroxide is used experimentally in biology to induce programmed cell death in isolated eukaryotic cells.

use

For neutralizing hydrogen peroxide in 2-component contact lens cleaners.

Individual evidence

  1. ↑ catalase.  In: Online Mendelian Inheritance in Man . (English).
  2. ↑ P. Chelikani et al., CMLS, Cellular and Molecular Life Sciences . 61 (2004), pp. 192-208; doi : 10.1007 / s00018-003-3206-5 (English)
  3. ↑ CD Putnam et al., Journal of Molecular Biology . 296 (2000), pp. 295-309; doi : 10.1006 / jmbi.1999.3458 (English)
  4. ↑ Information on the type or individual evidence is missing.
  5. ↑ Oliver Auferkamp: Investigation of the reaction mechanism of beef liver catalase . Duisburg / Essen 2007, p. 18 , urn : nbn: de: hbz: 465-20080305-090734-6 (dissertation, University of Duisburg-Essen).

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