Malate dehydrogenase: Difference between revisions
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<scene name='Malate_dehydrogenase/Active_site/1'>crevice</scene> for the substrate to bind. | <scene name='Malate_dehydrogenase/Active_site/1'>crevice</scene> for the substrate to bind. | ||
The mechanism of catalysis is dependent on <scene name='Malate_dehydrogenase/Active_site/2'>several invariant residues</scene>. These residues are HIS 195 and ASP 168 which are involved in hydrogen bonding, ASP 53 associated with NAD+ binding, and a triad of arginine residues at 102, 109, and 171. During the conversation of malate to oxaloacetate, a key conformational change occurs on the binding of substrate in which a “loop” flips into an up position to block the active site from the solvent. When this occurs, the other residues in the active site are brought closer to the substrate to enable the conversion. R102 and R109 are involved in this loop flip and thus invariant. After the loop flip, the malate complex is stabilized via hydrogen bonding before accepting a proton transfer from NADH to form oxaloacetate | The mechanism of catalysis is dependent on <scene name='Malate_dehydrogenase/Active_site/2'>several invariant residues</scene>. These residues are HIS 195 and ASP 168 which are involved in hydrogen bonding, ASP 53 associated with NAD+ binding, and a triad of arginine residues at 102, 109, and 171. During the conversation of malate to oxaloacetate, a key conformational change occurs on the binding of substrate in which a “loop” flips into an up position to block the active site from the solvent. When this occurs, the other residues in the active site are brought closer to the substrate to enable the conversion. R102 and R109 are involved in this loop flip and thus invariant. After the loop flip, the malate complex is stabilized via hydrogen bonding before accepting a proton transfer from NADH to form oxaloacetate <ref>PMID:7849603</ref>. | ||
The evolutionary past of MDH shows a divergence to form lactate dehydrogenase (LDH) which functions in a very similar way to MDH. Although there is a very low sequence conservation among MDH and LDH’s [http://blast.ncbi.nlm.nih.gov/Blast.cgi] the structure of the enzyme has remained relatively conserved. The key difference between the two is in the substate: LDH catalyzes pyruvate to lactate. | The evolutionary past of MDH shows a divergence to form lactate dehydrogenase (LDH) which functions in a very similar way to MDH. Although there is a very low sequence conservation among MDH and LDH’s [http://blast.ncbi.nlm.nih.gov/Blast.cgi] the structure of the enzyme has remained relatively conserved. The key difference between the two is in the substate: LDH catalyzes pyruvate to lactate. | ||