BROAD BEAN LIPOXYGENASE .1. PARTIAL-PURIFICATION AND CHARACTERIZATION

From locally grown large broad beans, active lipoxygenase preparations A, B and C were obtained by ammonium sulphate fractionation, Sephadex G-150 chromatography and Sephadex G-50 and Sephadex G-150 chromatography, respectively. All preparations were almost completely inhibited by 2 × 10-5M diethyldithiocarbamate. The inhibitors EDTA, 8-hydroxyquinoline 2,2-dipyridyl and 1:10 phenanthroline were found to inhibit preparations of different purities at various millimolar concentrations. Crude extracts and preparation C were found to be activated by calcium ions while preparation B was not. Further characterisation of preparation C showed that its optimum pH was about 6 and that it oxidised linoleic acid, methyllinoleate and trilinolein. The ester and triglyceride activity of the preparation could also be stimulated by calcium ions, such activations being greatest at pH 7. Amongst the soybean lipoxygenase isoenzymes so well characterised in the literature, isoenzyme 2 is activated by calcium ions, has an optimum pH near 6·5 and oxidises both linoleic acid and methyllinoleate. The preliminary results obtained, therefore, suggest that preparation C has isoenzyme 2 as an essential component. © 1979.