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A Practical Spectrophotometric Approach for the Determination of Lipoxygenase Activity of Durum Wheat

In this study, a practical spectrophotometric approach was used to determine the hydroperoxidation activity of durum wheat lipoxygenase (LOX). As stated in the related literature, the buffered linoleic acid solution used as the reaction medium is not optically clear enough at neutral and lower pH values due to its limited solubility. In our study, the optical clarity was obtained by the formation of sodium-salt of unreacted linoleic acid just before absorbance measurement. The durum wheat LOX was characterized in terms of pH and temperature optima as well as kinetic parameters. The maximum linoleic acid hydroperoxidation activities were determined at pH 5.0 and 6.5 and at 40°C This result can be considered as evidence for the presence of at least two LOX isoforms with respective optima at pH 5.0 and 6.5 in the crude durum wheat extract. The Michaelis constant (K_m) and maximum hydroperoxidation) activity rate (V_max) of durum wheat LOX for linoleic acid were estimated) to be 0.131 ± 0.019 mM and 42.37 ± 3.32 units/mg of protein/min, respectively. The method seems to be useful for the determination of LOX activity in durum wheat and its milling fractions.