CAT Protein – Catalase(CAT)

General information on CAT protein

CAT Protein also known as catalase is an enzyme located in almost all aerobically respiring organisms. Its main role is to catalyze the decomposition of hydrogen peroxide (H2O2) to water and oxygen in energy efficient manner. H2O2 is product of reactive oxygen species also known as ROS. ROS are chemical species that contain oxygen and are chemically reactive. ROS are byproducts of normal metabolism of oxygen and have important roles in cell signaling as well as homeostasis. Their levels can increase dramatically in times of environmental stress which can result in significant damage to cell structure. Hence, the catalytic activity of CAT protein is essential in protecting the cell from the byproducts of oxidative damage by reactive species. Catalase is located in all major sites of H2o2 production in the cellular environment such as peroxisomes, cytosol, mitochondria and even chloroplast).

At low H2O2 concentrations and the presence of small molecular electron donors such as alcohols, formats and nitrites, catalase can act as peroxidase which are a class of enzymes that catalyze oxidoreduction reactions. Other roles of catalase involves promoting the growth of normal and transformed fibroblast cells, immunity T-cells and B-cells as well as cancerous cells such myeloid leukemia cells, melanoma cells, mastocytoma cells.

CAT protein is a tetramer consisting of four polypeptide chains. The four polypeptide have iron-containing heme groups that allows the catalase to react with hydrogen peroxide. Depending on the catalase, the optimum pH may vary between 4 and 11. For human catalase the optimum pH is 7 with the rate of reaction not changing significantly between pH 6.8 and 7.5.

Altered catalase activity have been linked to a number of disorders. For instance, increased catalase activity has been observed in patients suffering from liver disorders, hemolytic diseases, acute pancreatitis, muscular dystrophies, and so forth (Goth, 1987). Decreased catalase activity has been linked with several diseases including malignant diseases, anemia, diabetes mellitus, and Down’s syndrome. (Djordjevic et al., 2000).

References:

• Goth, L. (1987). No catalase isoenzymes in serum. Clin. Chem. 33, 2302–2303.
• Djordjevic´, B. V., C´ osic´, V., Pavlovic´, D., Vlahovic´, P., Jevtovic´, T., Kocic´, G., and Savic´, V. (2000). Does captopril change oxidative stress in puromycin aminonucleoside nephropathy? Renal. Fail. 22, 535–544.