Calcium ion activation of lipoxidase

Fresh extracts of ground navy beans had very low activity for peroxidation of linoleic acid at pH 7.5. The addition of calcium ions to the reaction mixture prior to the addition of extract caused a large increase in the rate of production of linoleic acid hydroperoxides and diene conjugation. Calcium ions had no effect on the rate of production of hydroperoxides from linoleic acid at pH 5.5 or from a trilinolein substrate at either pH tested. Sodium deoxycholate and EDTA affected the rate of linoleic acid lipoxidase activity at pH 7.5 when calcium ions were present. Soybean extracts also possessed a calcium ion stimulated lipoxidase.