细胞定位：Peroxisome.
序列相似性：Belongs to the catalase family.
Catalase is a hemoprotein containing four subunits which decomposes peroxide.
Catalase is an enzyme responsible for the degradation of hydrogen peroxide. It is a protective enzyme present in nearly all animal cells.
This product
Specificity
The reaction of catalase occurs in two steps. A molecule of hydrogen peroxide oxidizes the heme to an oxyferryl species. A porphyrin cation radical is generated when one oxidation equivalent is removed from iron and one from the poryphyrin ring. A second hydrogen peroxide molecule acts as a reducing agent to regenerate the resting state enzyme, producing a molecule of oxygen and water.
Molecular Characteristics
The gene that encodes catalase, CAT, is located on chromosome 15 in Bos taurus. The gene is conserved in human, chimpanzee, dog, mouse, rat, chicken, zebrafish, fruit fly, mosquito, C. elegans, S. pombe, S. cerevisiae, K. lactis, E. gossypii, N. crassa, A. thaliana, and rice.
Composition:
Catalase is a tetramer consisting of four identical, tetrahedrally arranged subunits. Each 60 kDa subunit contains a heme group and NADPH in its active center.
Applications
Commercially wherever hydrogen peroxide is used as a germicide (Chu et al. 1975)
Milk preservative with peroxidase (Collins 1971)
Increases synthesis and stability of diacetyl in cultured milk (Collins 1971)
Free radical research (Lardinois 1995)
Deodorization (White and White 1997)
Decomposition of residual hydrogen peroxide after bleaching woven and knitted cotton fabrics before drying (White and White 1997)
Cysteamine determination (White and White 1997)
Gluconic and glycolic acid production (Seip et al. 1994, and Godjevargova et al. 2004)
Cleaning silicon and semiconductor plates (White and White 1997)
Characteristics of Catalase
Protein Accession Number: P00432
Molecular Weight:
232 kDa (Schroeder et al. 1969)
240 kDa (Herskovits 1969)
Monomer: 57.5 (Schroeder et al. 1969)
Optimal pH: Approximately 7.0 (Maehly and Chance 1954)
Isoelectric point: 5.4 (Samejima et al. 1962)
Extinction Coefficient: 246,000 cm⁻¹M⁻¹ (Theoretical); E1%, 276 = 12.9 (Herskovits 1969)
Active Site Residues: Histidine (H74), Asparagine (N147)
Activators: Sodium arsenate (Kertulis-Tartar et al. 2009)
Inhibitors:
Cyanide, azide, hydroxylamine, aminotriazole, and mercaptoethanol (Switala and Loewen 2002)
Ascorbate alone as well as with Cu²⁺ (Orr 1967a, b)
Freezing and lyophilization cause inactivation (Tanford and Lovrien 1962, and Deisseroth and Dounce 1967).
Inactivated by sunlight under aerobic conditions (Mitchell and Anderson 1965)
Peroxide (Altomare et al. 1974)
Nitro and nitroso compounds (Titov et al. 2008)
Catalase Assay
Method: Essentially that described by Beers and Sizer (1952) in which the disappearance of peroxide is followed spectrophotometrically at 240 nm.
One Unit decomposes one micromole of H₂O₂ per minute at 25°C and pH 7.0 under the specified conditions.
Reagents
0.05 M Potassium phosphate, pH 7.0
0.059 M Hydrogen peroxide (30%) in 0.05 M potassium phosphate, pH 7.0
Enzyme
Immediately prior to use dilute the enzyme in 0.05 M phosphate buffer, pH 7.0 to obtain a rate of 0.03-0.07 ΔA/min.
Procedure
Adjust the spectrophotometer to 240 nm and 25°C.
Pipette into each cuvette as follows:
Reagent grade water 1.9 ml
0.059 M Hydrogen peroxide 1.0 ml
Incubate in spectrophotometer for 4-5 minutes to achieve temperature equilibration and to establish blank rate if any. Add 0.1 ml of diluted enzyme and record decrease in absorbance at 240 nm for 2-3 minutes. Calculate ΔA240/min from the initial (45 second) linear portion of the curve.
Calculation
G2616240
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