Regulation of Gene Expression of Fatty Acid Synthetase in Euglena

脂肪酸合成酶（1型）是从叶绿体功能缺陷的绿叶草突变体中纯化得到的。采用硫酸铵和羟基磷灰石处理进行提纯。该脂肪酸合成酶不稳定，在纯化过程中失去了活性。经测试的几种试剂并没有阻止活性的丧失。研究了生长过程中CO_2浓度对小球藻11h脂质代谢的影响。其主要脂质为磷脂酰胆碱（PC）、磷脂酰乙醇胺（PE）、单半乳糖二酰甘油（MGDG）和双半乳糖二酰甘油（DGDG）。高co_2和低co_2细胞的脂类相对含量基本相同。低co_2细胞的脂肪酸不饱和程度高于高co_2细胞。18:2到18:3的比例变化尤为显著。在高co_2和低co_2细胞中，四种主要脂质18:2 / 18:3的比值不同。半乳糖脂的相对差异明显大于磷脂。与MGDG和DGDG结合的脂肪酸的去饱和发生在叶绿体中，与PC和PE结合的脂肪酸的去饱和发生在内质网中。CO_2浓度对前者活性的影响比对后者活性的影响更显著。在高co_2和低co_2细胞中，叶绿体和细胞质途径的贡献是不同的。

Fatty acid synthetase (Type 1) was purified from a mutant of Euglena gracilis which is defective in the function of chloroplasts. Purification was carried out by ammonium sulfate and hydroxyapatite treatments. This fatty acid synthetase was not stable and its activity was lost during the purification. Several reagents tested did not prevent the lost of the activity.We investigated the effects of CO_2 concentration during growth on the lipid metabolism in Chlorella vulgaris 11h. Major lipids of C. vulgaris was phosphatidylcholine (PC), phosphatidylethanolamine (PE), monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). The relative contents of lipid classes were essentially the same in high-CO_2 and low-CO_2 cells. However, the degree of unsaturation of fatty acids was higher in low-CO_2 cells than in high-CO_2 cells. The change in the ratio of 18 : 2 to 18 : 3 was particularly significant. The ratio of 18 : 2/18 : 3 in four major lipids was different between high-CO_2 and low-CO_2 cells. The relative differences were markedly greater in galactolipids than in phospholipids. In C. vulgaris, the desaturation of fatty acids bound to MGDG and DGDG occurs in chloroplasts and that of fatty acids bound to PC and PE occurs in endoplasmic reticulum. The former activity was affected by CO_2 concentration more remarkably than the latter activity. It is also suggested that the contributions of chloroplastic and cytoplasmic pathways were different between high-CO_2 and low-CO_2 cells.