Phospholipase C from Bacillus cereus. Action on Some Artificial Lecithins.

Abstract

The hydrolysis by phospholipase C [EC 3.1.4.3] from B. cereus of several lecithins of different fatty acyl chain length was examined. The enzyme showed significant activity towards monomolecularly dispersed short chain lecithins and the reaction obeyed normal Michaelis-Menten kinetics. Rate vs. substrate concentration curves obtained with dihexanoyl-., diheptanoyl-and dioctanoyllecithins showed marked discontinuities in the region of the known critical micelle concentrations for these substrates and distinctly higher rates were obtained just above these levels. Using these 3 lecithins at levels below their respective critical micelle concentrations, rate increases were noted if the reactions were allowed to proceed to a sufficiently great extent. The presence of deoxycholate in the reaction system had little or no effect on the rate of enzyme-catalyzed hydrolysis of lecithins of fatty acyl chain length .ltoreq. C8, but for fatty acyl chain lengths .gtoreq. C10, significant rate increases occurred. The pH profile for the enzyme activity was also examined.