Effects of temperature on the mitochondrial malate dehydrogenase of adult muscle of Toxocara canis.
Purified mitochondrial malate dehydrogenase isoenzyme (m-MDH) of Toxocara canis muscle presented maximum activity at 48 degrees C. A clear change in slope of the Arrhenius plot was observed. The energy of activation calculated for the catalytic process showed values of 3.2 kcal/mol and 10.5 kcal/mol. Thermal inactivation of m-MDH showed that it is more thermolabile than the s-isoenzyme. The inactivation of the enzyme by heat could be reduced at least in part by the addition of 0.1 mM NADH. The heat denaturation showed to be a first-order process. The rate constant (k) was calculated as being of the order of 5.28 X 10(-4) s-1 at 40 degrees C. The activation energy for the heat inactivation process was 16.45 kcal/mol between 30 degrees C and 40 degrees C and 13.79 kcal/mol between 40 degrees C and 48 degrees C.
Mansini
E
E
Departamento de Bioquímica, Universidade Federal do Rio de Janeiro, Brasil.
Oestreicher
E G
EG
Ribeiro
L P
LP
D000818:Animals; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000378:metabolism*; D008931:Mitochondria, Muscle / Q000201:enzymology; D011489:Protein Denaturation; D013696:Temperature; D013816:Thermodynamics; D014119:Toxocara / Q000201:enzymology*
D007527:Isoenzymes; D008291:Malate Dehydrogenase