Enzymatic catalysis via liquid-liquid interfaces

Enzymes acting in a biphasic liquid of water and organic solvent may show catalytic activity dependent on the amount of phase interface available. Such an effect may be caused by several mechanisms. For example, for hydroxynitrile lyase from Prunus amygdalus, substrate mass transfer limitation has been advocated, but also adsorption of the enzyme on the interface. In this commentary it is shown that often these two mechanisms will have qualitatively similar consequences. The reaction rate will be influenced by the organic substrate concentration, by the initial enzyme concentration, and by the volume-specific interfacial area, and these influences will be linear at low values but reach a saturation level at high values. To rule out any of the models, their quantitative mathematical descriptions should be compared, taking into account that both models may be valid simultaneously. (C) 2003 Wiley Periodicals, Inc.