Combined Action of Temperature and Pressure on the Catalytic Activity of Wild-Type and D70G Mutant of Human Butyrylcholinesterase

Abstract

The combined action of temperature and pressure on the catalytic activity of wild-type human butyrylcholinesterase (BuChE) and its D70G mutant were investigated. The D70 residue, located near the top of the active site gorge, is an important component of the peripheral anionic site of BuChE. Results showed a break in Arrhenius plots of wild-type BuChE (at about 22 °C) whatever the pressure, whereas no break was observed in Arrhenius plots of the D70G mutant. These results suggested a temperature-induced conformational change of the wild-type BuChE which does not exist in the D70G mutant. At 1 kbar, a transient state of wild-type BuChE, in which the substrate binding was reinforced, appeared but was not observed for the mutant. Hydration changes in the BuChE active site gorge could be involved in formation of this transient state. Results indicate that the D70 residue is involved in regulation of activity as a function of temperature and pressure.