Isolation of phospholipase A 2 from soybean ( Glycine max) seeds : The study of its enzymatic properties

Abstract

A protein with phospholipase A 2 (PLA 2) activity was isolated from soybean ( Glycine max) seeds. The affinity column chromatography techniques by using Cibacron Blue and immobilized substrate onto Eupergit C, were important steps in the purification protocol. The electrophoretic mobility showed by the purified enzyme, agreed with a molecular mass of 14 kDa. The PLA 2 activity against liposomes was determined by measurement of apparent absorbance changes at 340 nm. Also, high performance thin layer chromatography (HPTLC) analysis confirmed selective hydrolysis at the sn-2 position of soybean phospholipids. PLA 2 exhibited millimolar calcium dependence and had slightly alkaline pH optimum. The enzyme was stimulated by auxins and completely inactivated by ammonium sulfate. Furthermore, it was irreversibly inactivated by p-bromo-phenacyl bromide, the specific inhibitor of secretory PLA 2s. In addition, Glycine max PLA 2 showed high stability against heat treatment and organic solvents. The enzyme showed activity toward multilamellar vesicles of soybean phospholipids, with a V max = 950 U/mg and a K M = 0.78 mM. The hyperbolic behavior observed was coherent with a hopping mode of action, one of the two characteristic interfacial mechanisms of PLA 2s. All these data agree with the expected properties for a secretory PLA 2 being the first soybean enzyme of this type. The new PLA 2 developed lipolytic activity on a water in oil microemulsion reaction system, which is suitable for lysophospholipid production. These lysoderivatives are valuable biosurfactants for food and pharmaceutical industries.