Malate dehydrogenase: Difference between revisions

[[Malate dehydrogenase|Malate Dehydrogenase]] (MDH)(PDB entry [http://www.pdb.org/pdb/explore/explore.do?structureId=2X0I 2x0i]) is most known for its role in the metabolic pathway of the tricarboxylic acid cycle, also know as the Krebs cycle (after [http://en.wikipedia.org/wiki/Hans_Adolf_Krebs| Sir Hans Krebs]), which is critical to cellular respiration in cells [http://en.wikipedia.org/wiki/Citric_acid_cycle]; however, the enzyme is also involved on many other metabolic pathways such as glyoxylate bypass, amino acid synthesis, gluconeogenesis, and oxidation/reduction balance <ref>PMID:12537350</ref>. It is classified as an oxidoreductase[http://en.wikipedia.org/wiki/Oxidoreductase]. Malate dehydrogenase has been extensively studied due to its many isozymes <ref>PMID:20173310</ref>. The enzyme exists in two subcellular locations: mitochondria and cytoplasm. In the mitochondria, the enzyme catalyzes the reaction of malate to oxaloacetate; however, in the cytoplasm, the enzyme catalyzes oxaloacetate to malate to allow transport <ref>PMID:20173310</ref>. This conversion is an essential catalytic step in each different metabolic mechanism. The enzyme malate dehydrogenase is composed of either a dimer or tetramer depending on the location of the enzyme and the organism it is located in <ref>PMID: 9834842</ref>. During catalysis, the enzyme subunits are non-cooperative between active sites. The mitochondrial MDH suffers a complex allosteric control by citrate, but no other known metabolic regulation mechanisms have been discovered. Further, the exact mechanism of regulation has yet to be discovered <ref>PMID:7574693</ref>. The optimal pH is 7.6 for oxaloacetate conversion and 9.6 for malate conversion. The reported K_m value for malate conversion is 215 &micro;M and the V_max value is 87.8 &micro;M/min <ref>PMID:19277715</ref>. For halophilic MDH details, see [[Halophilic malate dehydrogenase]].  See also:<br />