Fumarase 2: Difference between revisions

Fumarase has the ability to catalyze the hydration of fumarate to malate or the dehydration of malate to fumarate.  The mechanism of fumarase in the hydration and dehydration reaction pathways remains simple, only involving three steps.  In the dehydration reaction, fumarase deprotonates a carbon atom on malate to form a carbanion (Beechmans 1998).  This deprotonation results in an aci-carboxylate intermediate (Weaver 2005).  After the intermediate forms, the acidic proton from the initial step removes the hydroxide group from the aci-carboxylate intermediate to form fumarase which then detaches from the active site of fumarase, completing the reaction (Rose, Weaver, 2004).  The active site binds with the substrate via Asn326 and Lys324 residues which function in the binding process.  The B site also can bind with S-malate, and the residues His129, Asn131, Asp132, and Arg126 contribute to binding (Weaver 2005).  The B site is located in a π-helix turn between the active site and solvent.  Two hydrogen bonds initiate the binding of Asn131 and Asp132 residues with S-malate (Rose, Weaver, 2004).