Metal-bindings Site of Pigeon Liver Malic Enzyme

Malic enzyme from pigeon liver is very sensitive to the metal-catalyzed oxidation, which results in rapid inactivation of the enzyme activity. The Fe^(2+)-mediated Fenten chemistry oxidizes and inactivates the enzyme, which is then specifically cleaved at the peptide bond between Asp-258 and Ile-259. Site-directed mutagenesis at the conserved Asp-258 confirmed that this aspartate residue is the metal binding ligand. This conclusion is corroborated by the crystal structure of human mitochondrial malic enzyme. Other metal ligands of the enzyme include Glu-234, Asp-235, C-1 carboxylate and C-2 hydroxyl of L-malate, plus a water molecule at the active site. Binding of metal ion induces a slow conformational change of the enzyme, which may represent a structural intermediate between the open- and closed-form. The functional role of the essential metal ion in the malic enzyme-catalyzed reaction is to position correctly the substrate L-malate in the active center and to stabilize the anionic enolpyruvate reaction intermediate.

並列關鍵字

malic enzyme ； metal site ； oxidative modification ； enzyme mechanism

國際替代計量

全文下載

主題瀏覽