Activation of liver microsomal glutathione S-transferase activity by heating.

The effect of heating on rat liver microsomal glutathione S-transferase activity was investigated. The microsomal glutathione S-transferase activity increased with an elevation of temperature and reached a maximal level at 50 degrees C for 30 min, at which point the enhancement was 2.6-fold. The microsomal glutathione S-transferase activity had one low Km value for 1-chloro-2,4-dinitrobenzene at room temperature. However, two Km values were observed in heated microsomes. N-Ethylmaleimide increased microsomal glutathione S-transferase activity 7.7-fold and a 2.5-fold increase in the activity was observed even after heating of microsomes at 55 degrees C for 10 min. On the other hand, there was no additional activation in the heated-microsomal glutathione S-transferase by glutathione disulfide or diamide with glutathione. The increased activity of the microsomal glutathione S-transferase activity is activated by heating through a mechanism different from the activation caused by sulfhydryl reagents.