Kinetic study of soybean pure powder lecithin hydrolysis using immobilized phospholipase A_2

摘要

Immobilized A_2 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: 45-48 deg C, 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 wand with the immobilized enzyme. The incubating time did not change the enzymatic acidivity. The hydrolytic activity of alumina or DEAE-sephadex adsorbed A_2 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 DEAE-sephadex respectively. For the same supports but at higher substrate concentration (25 mM) the zero order kinetic velocity constants were k = 1,62. 10~(-3) mol.l~(-1) (alumina) and k = 3,58. 10~(-3) mol.l~(-1).min~(-1) (DEAE-sephadex).