Thimann Laboratories, University of California, Santa Cruz, California 95064.
Plant Physiol. 1976 Apr;57(4):510-5. doi: 10.1104/pp.57.4.510.
Castor bean (Ricinus communis L. var. Hale) endosperms, excised after 2 days germination at 30 C, were incubated 5 min to 8 hr with (14)C-acetate and (3)H-glycerol. Homogenates were fractionated by sucrose gradient centrifugation. Organelles found to be active in lipid synthesis were the lipid bodies and the endoplasmic reticulum. The products of incorporation in the lipid bodies were (3)H-diglycerides containing (14)C-fatty acids of more than 20 carbons. In contrast, the endoplasmic reticulum produced (3)H-phospholipids as well as (3)H-diglycerides rich in (14)C-linoleate. The phospholipids synthesized and their acyl contents were of the types known to be the major components of organelle membranes in this tissue. Phospholipids and diglycerides containing (14)C and (3)H were found in the glyoxysomes and mitochondria subsequent to their appearance in the endoplasmic reticulum. The results show that germinating castor bean endosperm synthesizes membrane lipids de novo from acetate rather than reutilizing stored lipid components directly. It is also apparent that the endoplasmic reticulum is responsible for several steps in membrane lipid production.
蓖麻种子（Ricinus communis L. var. Hale）胚乳在 30°C 下发芽两天后取出，用（14）C-乙酸盐和（3）H-甘油在 5 分钟到 8 小时内进行孵育。匀浆通过蔗糖梯度离心进行分离。被发现活跃于脂质合成的细胞器是脂滴和内质网。在脂质体中掺入的产物是含有超过 20 个碳原子的（14）C-脂肪酸的（3）H-二甘油酯。相比之下，内质网产生（3）H-磷脂以及富含（14）C-亚油酸的（3）H-二甘油酯。合成的磷脂及其酰基含量是该组织中细胞器膜的主要成分。在它们出现在内质网之后，glyoxysomes 和线粒体中发现了含有（14）C 和（3）H 的磷脂和二甘油酯。结果表明，发芽的蓖麻种子胚乳从头合成膜脂，而不是直接重新利用储存的脂质成分。显然，内质网负责膜脂生产的几个步骤。
