The glycerolipid composition of pea (Pisum sativum L.) root plastids and their capacity to synthesize glycerolipids from [UL-14C]glycerol-3-phosphate were determined. Pea root plastids primarily consist of monogalactosyldiacylglycerol, triacylglycerol, phosphatidylcholine, digalactosyldiacylglycerol, and diacylglycerol. Maximum rates of total glycerolipid biosynthesis were obtained in the presence of 2.4 mM glycerol-3-phosphate, 15 mM KHCO3, 0.2 mM sodium-acetate, 0.5 mM each of NADH and NADPH, 0.05 mM coenzyme A, 2 mM MgCl2, 1 mM ATP, 0.1 M Bis-Tris propane (pH 7.5), and 0.31 M sorbitol. Glycerolipid biosynthesis was completely dependent on exogenously supplied ATP, coenzyme A, and a divalent cation, whereas the remaining cofactors improved their activity from 1.3- to 2.4-fold. Radioactivity from glycerol-3-phosphate was recovered predominantly in phosphatidic acid, phosphatidylglycerol, diacylglycerol, and triacylglycerol with lesser amounts in phosphatidylcholine and monoacylglycerol. The proportions of the various radiolabeled lipids that accumulated were dependent on the pH and the concentration of ATP and glycerol-3-phosphate. The data presented indicate that pea root plastids can synthesize almost all of their component glycerolipids and that glycerolipid biosynthesis is tightly coupled to de novo fatty acid biosynthesis. pH and the availability of ATP may have important roles in the regulation of lipid biosynthesis at the levels of phosphatidic acid phosphatase and in the reactions that are involved in phosphatidylglycerol and triacylglycerol biosynthesis.
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机译:测定了豌豆(Pisum sativum L.)根质体的甘油脂组成及其从[UL-14C] -3-磷酸甘油酯合成甘油脂的能力。豌豆根质体主要由单半乳糖基二酰基甘油,三酰基甘油,磷脂酰胆碱,二半乳糖基二酰基甘油和二酰基甘油组成。在存在2.4 mM甘油-3-磷酸酯,15 mM KHCO3、0.2 mM乙酸钠,NADH和NADPH各自为0.5 mM,0.05 mM辅酶A,2 mM MgCl2、1 mM ATP的情况下获得最大的总甘油脂生物合成速率,0.1 M Bis-Tris丙烷(pH 7.5)和0.31 M山梨糖醇。甘油脂的生物合成完全取决于外源提供的ATP,辅酶A和二价阳离子,而其余的辅因子将其活性从1.3倍提高到2.4倍。来自3-磷酸甘油的放射性主要在磷脂酸,磷脂酰甘油,二酰基甘油和三酰基甘油中回收,而在磷脂酰胆碱和单酰基甘油中的回收率较低。积累的各种放射性标记脂质的比例取决于pH值以及ATP和3-磷酸甘油的浓度。呈现的数据表明豌豆根质体几乎可以合成其所有成分甘油脂,并且甘油脂的生物合成与从头脂肪酸的生物合成紧密相关。 pH和ATP的可用性可能在调节磷脂酸磷酸酶水平上的脂质生物合成以及参与磷脂酰甘油和三酰甘油生物合成的反应中起重要作用。
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