title: Nucleotide sequence of the malate dehydrogenase gene of Thermus flavus and its mutation directing an increase in enzyme activity.
abstract: The nucleotide sequence of the malate dehydrogenase (mdh) gene from a thermophilic bacterium, Thermus flavus, was determined. The amino acid sequence of the Thermus malate dehydrogenase resembled that of the porcine heart cytoplasmic enzyme to a certain extent, and Asp-159 and His-187 were identified as possible essential residues for the catalytic function. The mutated mdh gene was also cloned from a spontaneous mutant of T. flavus containing a higher activity of the enzyme. Its mutation point was determined to be a single nucleotide exchange from C to T which caused Thr-190 to be substituted by isoleucine. The mutated enzyme showed resistance to substrate inhibition, an increase in both kcat and Km, and a shift toward a more acid optimum pH for the enzyme reaction.
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001483:Base Sequence; D007700:Kinetics; D046911:Macromolecular Substances; D008291:Malate Dehydrogenase / Q000235:genetics*; D009154:Mutation; D009206:Myocardium / Q000201:enzymology; D013552:Swine; D013824:Thermus / Q000201:enzymology* / Q000235:genetics
chemical_list: D000596:Amino Acids; D046911:Macromolecular Substances; D008291:Malate Dehydrogenase