Catalytic properties of lipoxygenase extracted from nine different Italian olive varieties (Olea europaea L.)

Lipoxygenases (linoleate oxygen oxidoreductase, LOX, EC 1.13.11.12) are a class of dioxygenases found abundantly in the plant kingdom, which catalyse the oxygenation reaction of polyunsaturated fatty acids (PUFA). Considering the capacity of LOX to define the distinctive and refined "green" fruity aroma of virgin olive oil (VOO), the biochemical study was conducted to characterise lipoxygenase in pulp and stone of nine Italian varieties of Olea europaea [Canino, Carboncella, Frantoio, Itrana, Leccino, Maurino, Moraiolo, Rosciola and Sirole]. The crude extracts were analysed to determine the kinetic parameters (V-max, K-M and V-max/K-M) and their optimum pH and temperature. The measurement of the catalytic activity of the LOX extracted from pulp and stones revealed the highly efficient catalytic activity of all the pulp samples from most of the analysed cultivars. Moreover, the kinetic analyses conducted on all olive samples revealed that the Frantoio pulp provided the best performance in terms of LOX activity. All crude extracts showed the highest oxidase activity at pH 6, while the values relating to the optimal temperature were obtained at 50 & DEG;C. The results provide valuable insight into optimising the VOO extraction process, particularly the kinetic parameters that could be useful tools to modulate the malaxation process.