Detection of two phospholipase A₂(PLA₂) activities in leaves of higher plant Vicia faba and comparison with mammalian PLA₂'s

Leaves of higher plant Vicia faba contains two Phospholipase A₂ (PLA₂) activities which are detected in cytosolic fractions. Based on a gel filtration column chromatography, two cytosolic PLA₂ activities migrated with molecular masses of 70 kDa and 14 kDa. The first (70 kDa peak) was optimally active at pH 4.5 and was not dependent on [Ca²⁺ for its activity. In the presence of 5 mM CaCl₂, 'phospholipase B' activity was shown in the 70 kDa peak. The second (14 kDa peak) was optimally active in the pH range 9-10 and required millimolar concentrations of calcium for optimal activity. The two activities were not inhibited by dithiothreitol. Neither anti-pancreatic PLA₂ antiserum nor anti-(pig spleen 100 kDa cytosolic PLA₂) antiserum immunoprecipitated any activity of the two plant PLA₂'s. The present results indicate that at least the 14 kDa form of the two PLA₂ enzymes detected in leaves of higher plants is biochemically and immunochemically different from the well characterized Ca²⁺-dependent mammalian PLA₂'s.