Department of Biochemistry and Statewide Air Pollution Research Center, University of California, Riverside, California 92521.
Plant Physiol. 1978 Mar;61(3):357-60. doi: 10.1104/pp.61.3.357.
Higher steryl ester biosynthetic activities were obtained with Triton X-100-phosphatidylcholine-cholesterol mixed micelles than with Tween 80-phosphatidylcholine-cholesterol mixed micelles when incubated with spinach leaf (Spinacia oleracea L.) acetone powder preparations. The best incorporation of [4-(14)C]cholesterol into [4-(14)C]cholesteryl ester was obtained with a Triton X-100-phosphatidylcholine-cholesterol (10:1:1, w/w) mixed micelle system. This mixed micelle system, however, required 1,2-dipalmitin and fatty acid-free bovine albumin for optimal activity. The reaction exhibited a diglyceride specificity since the dipalmitin requirement could be replaced with neither 1-monopalmitin nor tripalmitin. Significant amounts of steryl ester biosynthetic activity were detected in the chloroplast (1,000g pellet), mitochondrial (3,000g pellet), and microsomal (20,000g and 88,000g pellet) fractions. Little activity was detected in the water-soluble (88,000g supernatant) fraction. The highest specific activity occurred in the 88,000g pellet. The 88,000g supernatant contained a heatstable, water-soluble substance that was required for optimal steryl ester biosynthesis in all of the pellet fractions. This factor was not lost during extensive dialysis but was destroyed by ashing, indicating that it was large and organic. Silver nitrate thin layer chromatography indicated that 60% of the biosynthesized steryl esters contained saturated fatty acids in the absence of 1,2-dipalmitin and that 83% contained saturated fatty acids in the presence of 1,2-dipalmitin.
用Triton X-100-磷脂酰胆碱-胆固醇混合胶束与菠菜叶丙酮粉制剂孵育时，比用Tween 80-磷脂酰胆碱-胆固醇混合胶束获得更高的甾醇酯生物合成活性。用Triton X-100-磷脂酰胆碱-胆固醇（10：1：1，w/w）混合胶束系统获得了[4-（14）C]胆固醇掺入[4-（14）C]胆甾醇酯的最佳结合。然而，该混合胶束系统需要 1,2-二棕榈酸和无脂肪酸的牛白蛋白以达到最佳活性。反应表现出二甘油酯特异性，因为二棕榈酸的需求不能被 1-单棕榈酸或三棕榈酸替代。在叶绿体（1000g 沉淀）、线粒体（3000g 沉淀）和微粒体（20,000g 和 88,000g 沉淀）部分检测到大量的甾醇酯生物合成活性。在水溶性（88,000g 上清液）部分检测到的活性很少。最高的比活度发生在 88,000g 沉淀中。88,000g 上清液含有一种热稳定的水溶性物质，该物质是所有沉淀部分中甾醇酯生物合成的最佳所需物质。该因子在广泛的透析过程中不会丢失，但会被灰化破坏，这表明它是大而有机的。硝酸银薄层层析表明，在没有 1,2-二棕榈酸的情况下，60%的生物合成的甾醇酯含有饱和脂肪酸，而在存在 1,2-二棕榈酸的情况下，83%的甾醇酯含有饱和脂肪酸。
