High pressure-induced modulation of the activity and stability of Escherichia coli (lac Z) beta-galactosidase: Potential applications

High pressure in known to modulate both the activity and stability of enzymes. In the present work, the effect of pressure on the E. coli beta-galactosidase-catalyzed hydrolysis of the orthonitrophenylgalactopyranoside (oNPG) was investigated. Nucleophilic competition experiments were performed to determine the effect of pressure on the formation of the galactosylenzyme complex (Delta V-k2(#) = 0 +/- 4 ml mol(-1)) and its hydrolysis (Delta V-k3(#) = 20 +/- 2 ml mol(-1)). The inhibition of the reaction by various effectors was studied. High pressure was shown to modify the inhibition of the reaction by glucose and lactose. The variations observed might be related to the differences seen during the pressure-induced modulation of the two steps of the reaction. This allowed an explanation for the high pressure effect on E. coli beta-galactosidase-catalyzed reactions to be proposed. In parallel, the effect of pressure on the thermal stability of the enzyme was studied. Moderate pressure exerted a protective effect against thermal inactivation. The possibility of using high pressure to modulate both activity and stability of the enzyme is discussed. (C) 1997 by Elsevier Science Inc.