Fumarase C (fumarate hydratase) is an enzyme found in eukaryotic cells which catalyzes the reaction between L-malate and fumarate.[1] The catalysis proceeds via the deprotination of the C3 carbon of L-malate, which is followed by the loss of the -OH group attached to the C2 carbon; the intermediate for which is a carbanion transition state.[2] In order for this catalysis to occur L-malate must be bound to fumarase. Studies have determined that fumarase has two carboxylic binding sites (site-A and site-B) which could potentially be the active site for the conversion of L-malate to fumarate. Mutations of these sites were performed in order to determine their effects on the enzymatic activity of the fumarases. Specifically, the key histidines which were known to play an active role in the binding process were removed for each respective site. The results showed that a mutation of site-B lead to no statistical difference in specific activity when compared to wild type activity, while site-A's mutation lead to a significant decrease in enzyme activity. Thus, it was determined that binding site-A is in fact the active site for the conversion of L-malate to fumarate [3].
Binding Site Characteristics
Site-A: Site-A can be described as being comprised of atoms from three of the four sub-units (tetramer).
Site-B:
H188N: Effects of Mutation
H188N is used to refer to the mutation which replaced the H188 residue in site-A with asparagine.
H129N: Effects of Mutation
H129N is used to refer to the mutation which replaced the H129 rediue in site-B with asparagine.
Summary and Conclusions
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