[Characteristics of thermal inactivation of malate dehydrogenase].

Over the range 20-52 degrees C thermal inactivation of malate dehydrogenase (MDH) was studied with the aim of well grounded choice of its stabilization ways. The process was described by the pseudofirst order rate constants, kin, dependent on enzyme concentration. The rate constant of enzyme inactivation at the "infinite" dilution in general form equals 1.40 X 10(27) X exp (-43 000/RT) s-1, whereas at high enzyme concentration it is 1.26 X 10(8) X exp (-17 700/RT) s-1. The limiting step of the MDH inactivation is the enzyme dissociation into its subunits. In the concentrated enzyme solution a protein association is accompanied by its stabilization. The methods of characterization of oligomeric proteins dissociative inactivation are discussed.