[Characteristics of kinetics of phospholipid hydrolysis by phospholipase C from Bacillus cereus. Hydrolysis of phosphatidylcholine in the presence of deoxycholate].

Using dynamic light scattering and 31P-NMR spectroscopy methods, the reaction of solubilization of phosphatidylcholine by the ionic detergent, sodium deoxycholate, in aqueous solutions was studied. The kinetics of phosphatidylchodine hydrolysis by phospholipase C from B. cereus depending on the size and structural organization of substrate aggregates was investigated. No phosphatidylcholine hydrolysis was observed in the case of lamellar organization of the substrate, the size of lamellas not exceeding 2000-5000 A. The substrate hydrolysis rate within mixed micelles was controlled by the accessibility of the substrate on the surface of micellar aggregates. There was a decrease in the phosphatidylcholine hydrolysis rate at high detergent concentrations in the system. It was concluded that such a decrease in the hydrolysis rate can be due to two reasons, i) the decrease in mixed micelle size with a simultaneous decrease of surface concentration of the substrate, and, ii) the formation of "pure" detergent micelles capable to adsorb the enzyme by decreasing the "effective" concentration of phospholipase C.