The effects of MgCl2 and KCl on the structural properties of malate synthase from germinating soybean (Glycine max. L). were investigated. The enzyme was obtained from isolated glyoxysomes or from crude homogenates. It was clearly shown to undergo reversible structural interconversions depending on ionic strength as adjusted by MgCl2 and KCl (membrane bound enzyme form, precipitable aggregates, soluble dimeric and decameric forms). These interconversions were taken advantage of in the purification procedure.