Effect of Processing Conditions on Phospholipase D Activity of Corn Kernel Subcellular Fractions

The influence of physicochemical conditions on the phospholipase D (PLD) activity of subcellular preparations of sweet corn (Zea mays L. cv. Peaches and Cream) kernels has been studied. The microsomal, mitochondrial, and cytosolic preparations of corn kernels possessed PLD activity albeit at varying proportions. The microsomal and cytosolic PLD activities were stimulated 2-fold between 5 and 15 °C. Ethanol had varying modulatory effects on PLD activity. By contrast, acetaldehyde was a potent inhibitor of PLD. As well, a naturally occurring C6 aldehyde such as hexanal and an alcohol such as hexanol inhibited PLD activity efficiently. Divalent cations such as calcium chloride and magnesium chloride stimulated PLD activity at micromolar levels. Monovalent cations such as KCl and NaCl did not appear to affect PLD activity. Partial purification of PLD from the microsomal, mitochondrial, and cytosolic fractions separately revealed four major isoforms with relative molecular masses of 200, 140−150, 102−108, and 60−66 kDa. The importance of PLD in the maintenance of processed food quality is discussed. Keywords: Chilling; membrane; phospholipase D; processing; sweet corn kernels