Some properties of soybean lipoxygenase

Commercial soybean lipoxygenase (EC 1.99.2.1) was purified by ammonium sulfate fractionation, gel filtration on Sephadex G-150, and chromatography on DEAE-cellulose. The purified protein was essentially homogeneous as judged by acrylamide gel electrophoresis and ultracentrifugation. The molecular weight is 108,000 as determined by the sedimentation-equilibrium method. The amino acid composition was determined, and it was shown that the protein contains four residues of free sulfhydryl groups and four residues of half-cystine per molecule. Treatment of the protein with guanidine hydrochloride or sodium dodecyl sulfate produces dissociation. Present evidence indicates that the protein is composed of two subunits of 54,000 molecular weight.