INACTIVATION OF ENZYMES BY ORGANIC-SOLVENTS - NEW TECHNIQUE WITH WELL-DEFINED INTERFACIAL AREA

A liquid-liquid bubble column apparatus allows exposure of enzyme solu tions to water-immiscible organic solvents with a known total interfac ial area and well-defined time scales and flow. It allows clear distin ction of the different classes of inactivation mechanism. With urease as a model enzyme, octan-2-one and butylbenzene act only through the e ffects of solvent molecules dissolved in the aqueous phase, giving fir st-order inactivation at 0.34 and 0.21 h(-1), respectively. Hexane and tridecane act only through exposure to the interface. The amount of u rease inactivated is proportional to the total area of interface expos ed, rather than to elapsed time, and may be characterized by a rate of about 0.5 mu kat m(-2). This is consistent with the formation and (pa rtial) inactivation of a complete adsorbed monolayer of protein. With butan-1-ol, both mechanisms contribute significantly to the observed i nactivation. The presence of O-2 increases the rate of interfacial ina ctivation, but not that by dissolved solvent. (C) 1994 John Wiley & So ns, Inc.