title: Mitochondrial malate dehydrogenase from the thermophilic, filamentous fungus Talaromyces emersonii.
abstract: Mitochondrial malate dehydrogenase (m-MDH; EC 1.1.1.37), from mycelial extracts of the thermophilic, aerobic fungus Talaromyces emersonii, was purified to homogeneity by sequential hydrophobic interaction and biospecific affinity chromatography steps. Native m-MDH was a dimer with an apparent monomer mass of 35 kDa and was most active at pH 7.5 and 52 degrees C in the oxaloacetate reductase direction. Substrate specificity and kinetic studies demonstrated the strict specificity of this enzyme, and its closer similarity to vertebrate m-MDHs than homologs from invertebrate or mesophilic fungal sources. The full-length m-MDH gene and its corresponding cDNA were cloned using degenerate primers derived from the N-terminal amino acid sequence of the native protein and multiple sequence alignments from conserved regions of other m-MDH genes. The m-MDH gene is the first oxidoreductase gene cloned from T. emersonii and is the first full-length m-MDH gene isolated from a filamentous fungal species and a thermophilic eukaryote. Recombinant m-MDH was expressed in Escherichia coli, as a His-tagged protein and was purified to apparent homogeneity by metal chelate chromatography on an Ni2+-nitrilotriacetic acid matrix, at a yield of 250 mg pure protein per liter of culture. The recombinant enzyme behaved as a dimer under nondenaturing conditions. Expression of the recombinant protein was confirmed by Western blot analysis using an antibody against the His-tag. Thermal stability studies were performed with the recombinant protein to investigate if results were consistent with those obtained for the native enzyme.
authors.affiliation: Molecular Glycobiotechnology Group, Department of Biochemistry, National University of Ireland, Galway, Ireland.
authors.forename: Alan P
authors.initials: AP
authors.lastname: Maloney
authors.forename: Susan M
authors.initials: SM
authors.lastname: Callan
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Murray
authors.forename: Maria G
authors.initials: MG
authors.lastname: Tuohy
mesh_terms: D000595:Amino Acid Sequence; D015152:Blotting, Northern; D002845:Chromatography; D003001:Cloning, Molecular; D004926:Escherichia coli; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D012313:RNA / Q000032:analysis / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D032901:Talaromyces / Q000166:cytology / Q000201:enzymology* / Q000235:genetics*; D013696:Temperature
chemical_list: D011994:Recombinant Proteins; D012313:RNA; D008291:Malate Dehydrogenase