Subtypes
There are two classes of fumarases. Classifications depend on the arrangement of their relative subunit, their metal requirement, and their thermal stability. These include class I and class II. Class I fumarases are able to change state or become inactive when subjected to heat or radiation, are sensitive to superoxide anion, are Iron II (Fe2+) dependent, and are dimeric proteins consisting of around 120 kD. Class II fumarases, found in prokaryotes as well as in eukaryotes, are tetrameric enzymes of 200,000 D that contain three distinct segments of significantly homologous amino acids. They are also iron-independent and thermal-stable. Prokaryotes are known to have three different forms of fumarase: Fumarase A, Fumarase B, and Fumarase C. Fumarase C is a part of the class II fumarases, whereas Fumarase A and Fumarase B from Escherichia coli (E. coli) are classified as class I.
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