Sandbox Reserved 1058: Difference between revisions

[[Image:Active Loop Shift.png|250 px|right|thumb|'''Figure 2. Active Site Loop Shift.''' Binding of the ligand to the enzyme results in a conformational shift that facilitates the breakdown of isocitrate. The active site loop unbound is shown in wheat and the active site loop bound is shown in green.]][[Image:Active_Site_Hydrogen_Bonding.png|250 px|right|thumb|'''Figure 3. Active site residues hydrogen bound to a cofactor and the products of the catalyzed isocitrate reaction.''' Glyoxylate is shown in blue, succinate is shown in green, and the Mg²⁺ cofactor is shown in yellow.]]

[[Image:Active Site Residues.png|250 px|right|thumb|'''Figure 4. Active Site Residues.''' All eight active site residues necessary for catalysis of isocitrate are shown in slate. However, the protein shown is a C191S mutant of isocitrate lyase.]]

[[Image:Complete_Mechanism.PNG|250 px|left|thumb|'''Figure 6. Observed Mechanism for the Breakdown of Isocitrate by Isocitrate Lyase.''' His193 shifts the pKa of Cys191 and removes its proton. This allows Cys191 to extract a proton from the hydroxyl group of isocitrate. The resulting oxyanion forms a carbonyl and forces the lysis of a C-C bond. Glyoxylate and the enol form of succinate are formed and stabilized with a Mg²⁺ ion. The succinate enolate resonates and extracts the proton back from Cys191 to form succinate.]]