catalase

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Catalase (CAT), an enzyme that catalyzes the decomposition of hydrogen peroxide into oxygen and water, exists in the peroxidase of cells. Catalase is peroxisome Marker enzyme About 40% of the total peroxisome enzymes. Catalase exists in various tissues of all known animals, especially in the liver at a high concentration. Catalase is used in the food industry to remove hydrogen peroxide from milk used to make cheese. Catalase is also used in food packaging to prevent food from being oxidized.^[1]

Chinese name: catalase^[2]
Foreign name: CATALASE FROM MICROCOCCUS LYSODEIKTICUS
Alias: Catalase Isolated from Autohemolytic Streptococcus

Main role: Catalytic H two O two Decomposition into H two O and O two^[1]
Presence: In breathing organisms
Application: food , textile, etc

catalog

brief introduction

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Hydrogen peroxide (H2O2) is known as hydrogen peroxide. It has one more oxygen atom (0) than water (H2O). This oxygen atom is extremely unstable and always wants to take another oxygen atom from other material molecules to form O2. At ordinary times, we use hydrogen peroxide for sterilization and disinfection, because bacteria are destroyed by H2O2 and die. Bubbling during disinfection is the result of oxygen generation. However, hydrogen peroxide can penetrate most cell membranes, so it is better than superoxide anion Free radicals (unable to penetrate the cell membrane) have stronger cytotoxicity, which can react with iron in the cell after penetrating the cell membrane Hydroxyl radical 。 Catalase (CAT) is an important member of the antioxidant enzyme system, also known as catalase, which is a binding enzyme with iron porphyrin as the auxiliary group. SOD enzyme disproportionates oxygen free radicals to generate hydrogen peroxide (H2O2) and oxygen (O2). Hydrogen peroxide is still a substance with oxidant toxicity in the body. The role of catalase is to promote the decomposition of hydrogen peroxide into molecular oxygen and water, so that cells are free from the toxicity of H2O2. The mechanism of CAT acting on hydrogen peroxide is essentially the disproportionation of hydrogen peroxide. Only two H2O2 molecules meet CAT successively and collide with the active center, can the reaction take place. The higher the concentration of H2O2, the faster the decomposition rate. Almost all physiological organisms have catalase. It is widely found in breathing organisms, mainly in chloroplasts, mitochondria, endoplasmic reticulum of plants, as well as in liver and red blood cells of animals. Its enzymatic activity provides antioxidant defense mechanisms for the body. The biological function of catalase is to promote the decomposition of hydrogen peroxide in cells so that it will not further produce highly toxic hydrogen and oxygen free radicals, thus protecting the function of antioxidant enzyme system, which is also of great significance for human growth and metabolism.

Yan Shiying wrote that enzymes determine health, China Medical Science and Technology Press ,2015.12

hydrogen peroxide Enzymes exist in the peroxides in red blood cells and some tissues. Its main function is to catalyze the decomposition of H2O2 into H2O and O2, so that H2O2 will not react with O2 to produce very harmful - OH under the action of iron chelates

catalase

The role of catalase is to reduce hydrogen peroxide to water: 2H2O2=O2 ↑+2H2O

Chinese name: catalase^[2]

English alias: Fungal catalase; catalase from bovine liver; catalase F. bov. liv., cryst.susp. in H2O; Catalase from microorganisms; catalse from bovine liver; catalase from human erythrocytes; catalase from dog liver; catalase from mouse liver; catalase from bison liver; Catalase (bovine liver); Catalase, Human Erythrocytes; Catalase Aspergillus niger; Catalase from Corynebacterium glutamicum; Catalase Micrococcus lysodeikticus; Catalase

Color Molecular Structure Diagram

CAS:9001-05-2^[2]

EINECS:232-577-1^[2]

EC 1.11.1.6

Contact enzyme

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Catalase (CAT) is an enzyme scavenger, also known as catalase Iron porphyrin Auxiliary Conjugating enzyme 。 It can promote H2O2 to decompose into molecular oxygen and water, and eliminate hydrogen peroxide So as to protect cells from H2O2, which is a biological defense system key enzyme one of. The mechanism of CAT acting on hydrogen peroxide is essentially the disproportionation of H2O2. Two H2O2 must meet CAT successively and collide with active center Only when it is up, can the reaction take place. The higher the concentration of H2O2, the faster the decomposition rate.

Catabolic enzyme

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This is a stable hydrogen peroxide decomposing enzyme, which can decompose hydrogen peroxide into water and oxygen without affecting the fiber and dyes. Therefore, before dyeing after bleaching, residual hydrogen peroxide on the bleached fabric and in the dye vat is removed through H2O2 decomposing enzyme to avoid further oxidation of fiber and oxidation of dyes during dyeing. At the same time, the processing time can be shortened, the water for washing can be reduced, and the amount of wastewater can be reduced. It is especially suitable for yarns, bobbins and knitted fabrics. Similarly, the activity of catalase changes with the change of pH value and temperature, and the maximum activity is at about pH 7 and 30~40 ℃. Hydrogen peroxide concentration Increase, it will speed up decomposition reaction However, it must be noted that when the concentration is greater than a certain amount, the role of the enzyme will be weakened, so too much residual H2O2 is harmful to fibers and dyes. Therefore, the amount of H2O2 can not be increased arbitrarily because of the H2O2 decomposing enzyme. When using, it is usually necessary to pay attention to the compatibility of H2O2 decomposing enzyme with common surfactants and H2O2 stabilizers. The actual production application pH is 6~8, the temperature is 20~55 ℃, the amount of enzyme is 5~10KCLU/L, and the time is 10~20min. This technology has been gradually recognized and accepted in China, and it can improve reactive dye Brightness of color is very favorable.

source

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Catalase exists in almost all living organisms. It is generally found in breathing organisms, mainly in plants chloroplast 、 mitochondrion 、 Endoplasmic reticulum , animal liver and red blood cell Its enzymatic activity provides the body with antioxidant Defense mechanism.

CAT is a heme enzyme. Different sources have different structures. Its activity level varies in different tissues. The decomposition rate of hydrogen peroxide in liver is faster than that in brain or heart, which is due to the high level of CAT in liver.

reaction mechanism

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Although the complete catalytic mechanism of catalase has not been fully understood, its catalytic process is considered to be divided into two steps:

H2O2 + Fe(III)-E → H2O + O=Fe(IV)-E(.+)

H2O2 + O=Fe(IV)-E(.+) → H2O + Fe(III)-E + O2[12]

Wherein, "Fe() - E" represents the hemoglobin The central iron atom (Fe) of the group (E). Fe (IV) - E (.+) is a resonant form of Fe (V) - E, that is, the iron atom is not completely oxidized to+V valence, but receives some "support electrons" from heme. Therefore, heme in the reaction formula is also expressed as free radical cation (.+)

Hydrogen peroxide ingress Active site And at position 147 of enzyme Asparagine The interaction between the residue (Asn147) and the histidine residue (His74) at position 74 makes a proton stay Oxygen atom To each other. Free oxygen atoms coordinate and combine to form water molecule and Fe (IV)=O. Fe (IV)=O reacts with the second hydrogen peroxide molecule to form Fe (III) - E again, and generates water molecule and oxygen. [12] Active center iron atom The reaction activity may be due to the presence of the phenolic side chain of the tyrosine residue (Tyr357) at the 357 position (helping the oxidation of Fe (III) to Fe（ Reaction intermediate To improve its function. [12] The rate of this reaction can usually be determined by Michaelis equation To determine. [2]

Catalase can also oxidize other cytotoxic substances, such as formaldehyde formic acid , phenol and ethanol. These oxidation processes need to be completed by hydrogen peroxide through the following reactions:

H2O2 + H2R → 2H2O + R

Similarly, the specific reaction mechanism is still unclear.

Any heavy metal ion (such as copper ion in copper sulfate) can be used as a non Competitive inhibitor 。 In addition, the highly toxic cyanide is a competitive inhibitor of catalase, which can be tightly bound to the heme in the enzyme to prevent catalytic reaction 。

The three-dimensional structure of the catalase intermediate in the peroxide state has been analyzed and can be found in Protein database Retrieved from.

testing

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Bubbles can be observed during the catalase detection.

Catalase detection is one of the three main detection methods for microbiologists to identify bacterial species, that is, hydrogen peroxide is used to detect the existence of catalase. If the bacteria contain catalase Hydrogen peroxide solution The formation of oxygen bubbles can be observed by adding a small amount of bacterial extract into the.

If bubbles are formed, the bacterium is considered to be "catalase positive". For example, staphylococcus and micrococcus. If no, the bacterium is considered to be "catalase negative". For example, streptococcus and enterococcus. Although catalase detection cannot identify specific organisms, it can effectively help diagnosis when combined with other detection methods.

In addition, the presence of catalase in bacteria also depends on Cell growth Conditions and media used.

distribution

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Catalase exists in various tissues of all known animals, especially in the liver at a high concentration. stay bombardier beetle (Bombardier beer), catalase has a unique use. The beetle has two sets of chemicals stored separately in glands. Large glands store hydroquinone And hydrogen peroxide, and small glands store catalase and Horseradish peroxidase 。 When the beetle mixes the chemicals in the two glands together, it will release oxygen, which can both oxidize hydroquinone and act as a booster.

Catalase is also commonly found in plants, but it does not include fungi, although some fungi are found to be able to produce this enzyme in low pH and warm environments.

most Aerobic microorganism Both contain catalase [4] 。 Exceptions include Streptococcus , an aerobic bacterium without catalase. part Anaerobic microorganism , such as Methanosarcina barkeri It also contains catalase.

application

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Catalase is used in food industry to remove and manufacture cheese Hydrogen peroxide in milk. Catalase is also used in food packaging to prevent food from being oxidized. In the textile industry, catalase is used to remove hydrogen peroxide from textiles to ensure that the finished product is free of peroxide Of. It is also used in contact lenses Cleaning: After soaking glasses in a detergent containing hydrogen peroxide, use catalase to remove the residual hydrogen peroxide before use. The use of catalase in the beauty industry: some facial treatments have added this enzyme and hydrogen peroxide in order to increase epidermis The amount of oxygen in the upper cells.

Catalase is also often used in the laboratory to understand the enzyme pair reaction rate Tools affected.

function

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Function Overview

Hydrogen peroxide is a kind of waste produced in the metabolic process, which can cause damage to the body. In order to avoid such damage, hydrogen peroxide must be quickly converted into other harmless or less toxic substances. Catalase is often used by cells to catalyze the decomposition of hydrogen peroxide.

However, the true biological importance of catalase is not so simple: researchers found that the genetically engineered mice with catalase deficiency are still normal phenotype, which indicates that catalase is essential to animals only under certain conditions.

The level of catalase in some people is very low, but there is no obvious pathological reaction. It's probably normal Mammalian cell The main hydrogen peroxide scavenger in the Peroxide reductase (peroxiredoxin), not catalase.

Catalase is usually located in a Peroxisomes Of Organelle Medium. plant cell The peroxisomes in Photorespiration (use oxygen and produce carbon dioxide) and Symbiosis Nitrogen fixation (will nitrogen (N2) dissociated into Active nitrogen Atom).

But cells are pathogen When infected, hydrogen peroxide can be used as an effective anti micro Biological reagent 。 Some pathogens, such as Mycobacterium tuberculosis 、 Legionella pneumophila and Campylobacter jejuni , can produce catalase to degrade hydrogen peroxide, so that they can host Survival in the body.

Bleaching

It should be noted that enzyme can promote bleaching. Wool contains protease Bleaching in hydrogen peroxide bleaching solution of Bactosol ST can significantly improve the whiteness and hydrophilicity of wool. This is due to enzyme promotion Wool fibre The initial rapid erosion makes wool bleaching easier. Based on this principle, the wool is pretreated with protease to make the fiber surface bare, and then bleached. Obviously, the effect is better, and the fiber damage is easy to control.

history

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As a substance, catalase was first discovered by Louis Jacques Th é nard, the discoverer of hydrogen peroxide (H2O2), in 1811. In 1900, Oscar Loew named this enzyme that can degrade hydrogen peroxide "catalase", namely catalase, and found that this enzyme exists in many plants and animals. In 1937, James B· Sumner The catalase was crystallized from bovine liver, and the molecular weight of the enzyme was obtained in the next year. In 1969, bovine catalase amino acid The sequence is solved. Then, in 1981, its three-dimensional structure was analyzed.

Related diseases

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Peroxidase Peroxisomal disorder (acatasia) is caused by the functional defect of catalase.

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