EVIDENCE OF PHOSPHOLIPASE-ACTIVITY IN PHOSPHOLIPID-BILAYERS UNDER CONDITIONS OF LOW HYDRATION

Free fatty acids accumulate in the cell membranes of plant organs, suc h as seeds and pollen, that undergo periods of dry storage. Loss of vi ability in some of these tissues is,correlated with high levels of fre e fatty acids, causing the appearance of gel-phase domains and increas ing the leakage of cytoplasmic solutes. This free fatty acid productio n has been most often attributed to free-radical-mediated deesterifica tion of the phospholipids because the water content of these organisms was assumed to be too low to support enzyme activity. The present stu dy shows that phospholipases can be active in liposomes with partial r ehydration after freeze drying. This activity is seen with rehydration at only 20% relative humidity, allowing the possibility of enzyme act ivity in desiccated organisms.