title: Purification and properties of mitochondrial malate dehydrogenase of Toxocara canis muscle.
abstract: Mitochondrial malate dehydrogenase was purified from muscle extracts of Toxocara canis by means of Sephadex G-100 gel filtration, DEAE-Sephadex ion-exchange chromatography and 5'AMP-Sepharose 4B affinity chromatography. The purified enzyme showed an optimum pH for the reduction of oxaloacetate of 7.3 in Tris-HCl buffer and of pH 7.5-7.8 in phosphate buffer. The m-MDH showed values of 3.2 kcal/mol and 10.5 kcal/mol for the energy of activation, calculated from the Arrhenius equation. The mitochondrial enzyme was found to be more susceptible to thermal inactivation as compared with the cytosolic isoenzyme. Kinetic experiments showed that the m-MDH of Toxocara canis is inhibited by excess oxaloacetate but not by excess NADH. The apparent Km for oxaloacetate reduction was 53 microM and 0.54 mM for L-malate oxidation.
mesh_terms: D000818:Animals; D004285:Dogs; D007421:Intestine, Small / Q000469:parasitology; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000302:isolation & purification* / Q000378:metabolism; D008931:Mitochondria, Muscle / Q000201:enzymology*; D013816:Thermodynamics; D014119:Toxocara / Q000201:enzymology* / Q000302:isolation & purification
chemical_list: D008291:Malate Dehydrogenase