Evidence of phospholipase activity in phospholipid bilayers under conditions of low hydration

Free fatty acids accumulate in the cell membranes of plant organs, such as seeds and pollen, that undergo periods of dry storage. Loss of viability in some of these tissues is,correlated with high levels of free fatty acids, causing the appearance of gel-phase domains and increasing the leakage of cytoplasmic solutes. This free fatty acid production has been most often attributed to free-radical-mediated deesterification of the phospholipids because the water content of these organisms was assumed to be too low to support enzyme activity. The present study shows that phospholipases can be active in liposomes with partial rehydration after freeze drying. This activity is seen with rehydration at only 20% relative humidity, allowing the possibility of enzyme activity in desiccated organisms.