Isolation and Characterization of Lipoxygenase from Sponge Gourd (Luffa aegyptiaca)

Lipoxygenase (Linoleate: oxygen oxidoreductase EC.1. 13. 11. 12), a dioxygenase catalyzing the hydroperoxidation of fatty acids containing a cis,cis- 1,4-pentadiene structure was isolated from defatted whole and dehulled seeds of Luffa aegyptiaca ,a local plant found growing wildly in waste lands and rubbish dumps. Several properties of the enzyme including effect of pH, substrate concentration and heat treatment were investigated and lipoxygenase activity was determined spectrophotometrically at 234nm. Optimal activity was found at pH 6 and 7 and a linoleic acid concentration of 3.0mM and 3.5mM for the whole and dehulled seeds respectively. The values of Michalis-menten constant (km) and Vmax were determined as 1.563mM and 344.8 units ml-1 mm-1 for the whole seed and 1.724mM and 2083 units ml-1 mm-1 for the dehulled seed. The energy of activation for both the whole and dehulled seeds were obtained as 28.3 kJ mol-1 and 10.8 kJ mol1 respectively. Lipoxygenase activity was found to increase at the temperature 60 oC and 50 oC for the whole seed and the dehulled seed respectively.