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Biochemistry: Enzyme Index
(Ref.: Sci.Amer. (1983):C.de Duve "Microbodies in the living cell" May pp 52-77)
Activity and distribution
Although catalase has been intensively studied, its role in biological oxidation reactions is not known with certainty. Since it is found in the microbodies of some cells (both plant and. animal) it is believed to catalyse the decomposition of hydrogen peroxide in those structures. Hydrogen peroxide is a poisonous by-product of oxidative reactions in the cell and catalase is classed as a peroxidase.
Reaction catalysed by catalase
The role of catalase
Hydrogen peroxide is a poisonous compound and it must be broken down if it starts to build up in the cell. The major source of hydrogen peroxide in the cell is from the oxidation of flavin-linked oxidases:
This takes place in the microbodies of plant and animal cells. So it is not surprising to find catalase activity high in these cell organelles. Peroxysomes and glyoxysomes are microbodies found in the cells of plants and. fungi, whilst similar microbodies are found in animal cells, especially in liver and kidney tissues of mammals.
Structure of catalase
Catalase contains an iron cofactor bound in a prosthetic haem (aka heme) group (like haemoglobin and. the cytochromes)
Cofactors of enzymes
Cofactors may be loosely bound so that:
Or they may be very tightly bound to the enzyme = a PROSTHETIC GROUP.
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