Production of free fatty acids in marine phytoplankton

在20℃的间歇培养体系中，对赤潮的致病性浮游植物——三角藻（Paeodactylum tricornutum）和鞭毛藻Heterosigma akashiwo进行了游离脂肪酸（FFA）和磷脂酶A （PLaseA）活性的测定，发现三角藻在对数中期、固定早期和固定后期分别含有总脂肪的16%、29%和46%的FFA；伴随着大量的极性脂质（PL）和少量的三酰甘油（TG）、碳氢化合物和甾醇。在较低温度（5C）下，各生长阶段的游离脂肪酸含量分别降至1%、18%和32%。FFA的组成比为20:5 (n-3). h。在相同的培养体系中，在20℃条件下，赤禾在每个生长阶段的总脂质中仅含有2-4%的FFA，而PL含量超过90%。甘油三酯仅在静止后期含有，占总脂质的3%。FFA的主要成分为16:0和20:5 （n-3）。这些脂肪酸主要分布在单半乳糖二酰基甘油分子的sn-1位置，这是赤禾的主要脂类。另一方面，在磷脂酰胆碱分子中，20:5 （n-3）分布在sn-1和sn-2两个位置。三角草和赤石草制备的丙酮粉对二酰基磷脂酰胆碱具有PLaseA活性，而对TG几乎没有脂肪酶活性。因此，这两种浮游植物中的游离脂肪酸似乎主要是通过PLaseA从PL释放的。讨论了PLaseA1比PLaseA2更强的活性。

Determination of made of free fatty acids (FFA) and phospholipase A (PLaseA) activity in the diatom Paeodactylum tricornutum and the raphidophyte flagellate Heterosigma akashiwo, which is a causative phytoplankton of red tides.P.tricornutum in the mid-logarithmic phase, early stationary phase and late stationary phase in a batch culture system at 20C was found to contain 16,29 and 46% FFA of total lipid, along with larger amounts of polar lipids (PL) and smaller amounts of triacylglycerols (TG), hydrocarbons and sterols. At a lower temperature (5C), the FFA content in each growth phase was reduced to 1,18 and 32%, respectively. FFA composition was characterized by much 20 : 5 (n-3).H.akashiwo in the same culture system as P.tricornutum at 20C was found to contain only 2-4% FFA of total lipid in each growth phase, along with PL of more than 90%. TG was contained only in the late statinary phase, accounting for 3% of total lipid. Major components of FFA were 16 : 0 and 20 : 5 (n-3). These fatty acids were predominantly distributed in the sn-1 position of monogalactosyldiacylglycerol molecules, which were a major lipid class of H.akashiwo. In phosphatidylcholine molecules, on the other hand, 20 : 5 (n-3) was distributed in both sn-1 and sn-2 positions.Acetone powders prepared from P.tricornutum and H.akashiwo showed PLaseA activity toward dioleoylphosphatidylcholines and virtually no lipase activity for TG could be detected. Free fatty acids in the both phytoplanktons would thus appear to released primarily from PL by PLaseA.The greater activity of PLaseA1 compared to PLaseA2 is discussed.