Inhibition of Lipolysis by Normal Alcohols

The hydrolysis of methyl oleate by pancreatic lipase (EC 3.1.1.3) is inhibited by added normal alcohols. The efficiency of inhibition increases with the chain length of the alcohol, attaining a maximum at 10 carbon atoms. A further increase in chain length causes no further increase in inhibitory action. The data have been successfully treated by assuming that the reaction occurs at an interface. The inhibitory action of the alcohols followed the pattern of a typical Langmuir adsorption isotherm. The calculated free energy of adsorption of each —CH2— group of the alcohol was 820 cal. Although the uninhibited reaction was enzyme-limited, the effect of the alcohols could be overcome by the addition of more substrate, but not by the addition of more enzyme. It is concluded that the inhibiting effect of alcohol is due to its adsorption on the substrate, thus blocking the enzyme from the substrate. Some of the properties of ester hydrolysis, which result from the reaction taking place at an oil-water interface, are discussed.