Comparison of lipoxygenase activity characteristics in aqueous extracts from milk-stage sweet corn and waxy corn

Lipoxygenases (LOX) in milk-stage sweet corn and waxy corn were extracted using a phosphate buffer (pH 7.0) and enzyme activities were determined using linoleic acid as a substrate. Michaelis constant ( K m) values, decimal reduction times (D value), temperature sensitivity parameters (Z value), and activation energies ( E a) were calculated. Enzymes from both corn types followed first-order inactivation kinetics within 0–25 min and 50–70°C. However, enzymes exhibited different pH profiles and affinities toward linoleic acid. Km values (4.34 and 1.40 mM for sweet corn and waxy corn, respectively), heat stability values, and Ea values (116.81 and 246.82 kJ/mol) were different. Waxy corn LOX was more heat stable below 65–C with a higher D value, but was more temperature sensitive with a lower Z value. The different characteristics suggested the presence of different isoenzymes and necessitated the use of different parameters for blanching.