Catalase (CAT) is an enzyme crucial to immune and developmental systems. One of the first enzymes in many biological disciplines is catalase. But it has lots of weird features too. One of the highest turnover rates of any enzyme. It is necessary to eliminate poisonous hydrogen peroxide in nature and the industries of dairy, textiles, and drugs. Catalase is a cell antioxidant that neutralizes cell damage caused by oxidative stress, by assisting in the breakdown of hydrogen peroxide (H2O2) into water and oxygen. It does this to maintain the redox status of cells and guard cells from oxidative damage. Catalase controls cellular redox state and the function of cell signaling pathways. Catalase can modulate intracellular levels of hydrogen peroxide, modulating several cell signaling networks.
Proper amounts of hydrogen peroxide are essential to cell death. Catalase can influence the intracellular level of hydrogen peroxide, and thus cell death. This is necessary for the physiological function of tissues and organs. Catalase, also involved in immune control, functions in the immune system as well. With Catalase, pathogens detoxify hydrogen peroxide, immune cells function, and protect the body from outside damage.
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Necessity of Catalase
There are three categories of catalase - monofunctional catalase, bifunctional catalase-peroxidase, and manganese catalase. CAT, like superoxide dismutase and glutathione peroxidase, works as part of a defense mechanism against oxidative changes in DNA, proteins, and lipids by suppressing the free radical chain reaction in the body. So catalase gets involved in the dismutation of hydrogen peroxide H2O2 (a carcinogen that's deadly to living cells) into oxygen and water, most likely through a two-step molecular process:
H2O2 + Mn -E → H2O + O = Mn+1 -E( +. ) H2O2 + O = Mn+1 -E( +. ) → H2O + Mn -E + O2
In which M is the oxidized metal ion (manganese Mn2 (n = 2) or iron Fe (n = 3)) and ME is the rest of the enzyme (E) that has the manganese/heme centre. Also, these enzymes could use H2O2 to oxidise toxins like alcohol, phenols, formaldehyde and formic acid:
H2O2 + H2R → 2H2O + R
Physiological Activities of Catalase
Catalase is an important enzyme. It turns out that catalase is one of the earliest enzymes in biological sciences. Plant growth and defence systems are managed by the CAT protein family. CAT proteins can undergo all kinds of PTMs that change activity, ligand-binding, stability, compartmentalisation and function. This CAT interactome includes a host of cytoplasmic and nuclear proteins that seem necessary for protein function. Catalase is an essential enzyme with multiple physiological roles within cells, such as redox reactions, antioxidants, cell signalling, and apoptosis. Its activity must be regulated for intracellular homeostasis and body wellbeing. The physiological functions catalase plays include a host of them:
| Redox reactions |
Catalase can break down hydrogen peroxide (H2O2) into water and oxygen. This catalysis is a redox reaction that balances intracellular redox. |
| Antioxidant effect |
As an antioxidant enzyme catalase removes harmful oxidizing agents in the cell like hydrogen peroxide and thus minimizes the damage of oxidative stress on cells. |
| Participation in cell signaling |
Catalase is a cell signalling player too. A crucial signalling molecule in cells is hydrogen peroxide. The catalase's activity can alter cell levels of hydrogen peroxide and thus the cell signalling pathway. |
| Controlling cell death |
Catalase also has cell death. Right-sized amounts of hydrogen peroxide control cell death, and the catalase activity can affect cell hydrogen peroxide levels and so cell death. |
CAT transcription
In plants, CAT proteins are generally written by small gene families. For instance, three members of the CAT family in Arabidopsis express themselves in tissues that are partially similar to one another. CAT1 is abundant in pollen and seeds, CAT2 is the dominant photorespiratory CAT form and abundant in green tissues, and CAT3 is abundant in vascular tissues and dying organs. A number of transcription factors control CAT gene expression. GBF1 dysregulated CAT2 expression and inducing hypersensitivity. Unexpectedly, GBF1 up-regulates phytoalexin deficiency 4 (PAD4), a key enzyme for salicylic acid (SA) and phytoalexin synthesis.
Fig. 1 Catalase transcriptional regulation (Baker, A., et al. 2023).
Post-transcriptional Regulation
Alternative splicing is another control that can make several protein isoforms from the same gene. Alternative splicing, also called intron retention and exon skipping, is common in plants and is widely reported today. It is possible to produce a version of the CAT2 protein without the C-terminal 18 amino acids to correct all observed phenotypes of the cat2-1 mutant.
Protein Folding and Maturation
Nitric oxide (NO) prevents heme from inserting into various heme proteins, such as CAT, in mammalian cells. When heme synthesis is blocked, tetrameric CAT is not produced as well. Furthermore, the nitrosylated version of glyceraldehyde 3-phosphate dehydrogenase (SNO-GAPDH) inhibits heme insertion via NO. GAPDH Mutation: Cys152 blocks heme insertion. TRX 1 denitrosylates SNO-GAPDH and regulates NO's insertion of heme into CAT proteins.
Immunity and Programmed Cell Death
CAT also helps plants defend themselves against biotic and abiotic stresses. Every CAT isoform has CAT-dependent PCD responses. CAT3 and other CAT isoforms communicate with LESION SIMULATING DISEASE1 (LSD1), a key negative regulator of PCD in Arabidopsis. This combination manages SA build-up, photosensitive runaway PCD, and hypersensitive cell death. CAT is an effector protein, and CAT proteins engage with so many other proteins from countless subcellular locations.
Catalase Levels and Biomedical Relevance
Catalase levels: this is the activity of catalase in the organism, and its level changes have a major biomedical impact on an organism's health and disease states. The cell's antioxidant enzyme catalyzes the breakdown of hydrogen peroxide into water and oxygen, thus preventing the cells from being damaged by oxidative stress. Low catalase can cause more oxidative stress, which in turn degrades cells and tissues, and contributes to some of the disease states. Fluctuations in catalase are used to diagnose and treat some diseases. For instance, some tumors might have an abundance or excess of catalase and thus measuring and tracking catalase can be useful for the diagnosis and treatment of tumors.
As an inflammatories and immune system, catalase also participates. Increases or decreases in catalase can influence the activity of immune cells and the development of inflammatory processes, thereby affecting the body's resistance to infection and inflammation.
Conclusion
Catalase is involved with the immune system, especially eradicating free radicals and oxidative stress. When the body is invaded or infected by the outside world, catalase in the immune system breaks down hydrogen peroxide (H2O2) into water and oxygen, which eliminates dangerous oxidative molecules and guards cells against injury. The formation of organisms is also helped by catalase. It is involved in cell proliferation, differentiation, and death. By controlling intracellular hydrogen peroxide, catalase can dictate how and whether cells develop, and what they will eventually become, and it is an essential factor in the normal growth of living things.
All things considered, the relevance of catalase to immunity and development is its function in organismal homeostasis, cell protection from oxidative stress, and regulation of development.
References
- Baker, A., et al. Catalase: A critical node in the regulation of cell fate. Free Radical Biology and Medicine. 2023, 199: 56-66.
- Grigoras, A., et al. Catalase immobilization-A review. Biochemical Engineering Journal. 2017, 117: 1-20.
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