Kinetic study of soybean pure powder lecithin hydrolysis using immobilized phospholipase A2

Abstract

Immobilized A₂ phospholipase enzyme promotes the hydrolytic reaction of pure powder soybean lecithin releasing a mole of fatty acid from C-2 position. The main purpose of this paper was to determine the kinetic parameters of this reaction when the enzyme was adsorbed on alumina or DEAE-sephadex. The best conditions for the reaction were: temperature: 45-48ºC, Ca ions concentration: 6mM, pH: 8,65. Tested conditions for substrate concentration were: 6,3; 12,7; 19 and 25 mM working in a batch type reactor and with the immobilized enzyme. The incubating time did not change the enzymatic activity. The hydrolytic activity of alumina or DEAE-sephadex adsorbed A₂ phospholipase enzyme was lower than of the soluble enzyme because the intrinsic properties are modified by immobilization. For substrate concentrations ranging between 6 and 19 mM first order kinetic velocity constants were k = 9, 88. 10^-2 min^-1 and k = 1,766. 10^-1 min^-1 for alumina and DEAEsephadex respectively. For the same supports but at higher substrate concentration (25mM) the zero order kinetic velocity constants were k= 1,62. 10^-3 mol.l^-1min^-1 (alumina) and k = 3,58. 10^-3 mol.l^-1 min^-1 (DEAE-sephadex).