Evaluation of diffusional effects on kinetics of soybean lecithin hydrolysis using A2 phospholipase

Abstract

Soluble or immobilized A₂ phospholipase liberates one mole of fatty acid of the C-2 position in soybean lecithin phospholipids to product lysolecithins. When using the enzyme in its immobilized form the enzymatic activity decreases due to substrate and product transport phenomenon. By comparison of the kinetic parameters of the hydrolysis reaction catalized by A₂ phospholipase immobilized on alumina or on DEAE-Sephadex against those of the soluble enzyme, for soybean lecithin hydrolysis reaction, the diffusive effects were evaluated. The decrease of the reaction rate was quantified in presence of diffusive effects and the effectiveness factors were calculated. The Michaelis-Menten kinetic parameters were determined: K_M = 8,2.10-² mol·l^-1 and 5,36.10^-2 mol·l^-1 and V_max = 7,7.10^-5 mol·l^-1 .min^-1 and 9,5.10^-5 mol·l^-1 ·min^-1 for the enzyme immobilized on alumina and on DEAE-Sephadex, respectively. The effectiveness factors were 0,277 for alumina and 0,376 for DEAE-Sephadex.