Michaels A S, Jelsema C L, Barrnett R J
J Ultrastruct Res. 1983 Jan;82(1):35-51. doi: 10.1016/s0022-5320(83)90095-3.
We have cytochemically localized the acyltransferase activities in the alga Chlamydomonas reinhardtii. Glycerol 3-phosphate (G3P) acyltransferase and lysophosphatidate (LPA) acyltransferase activities were cytochemically assayed utilizing biochemically optimized reaction conditions (Jelsema et al., 1982). The cytochemical assays clearly demonstrate that in the wild-type cells (137+) and the y-1 mutant, both enzymes were present in the photosynthetic membranes, envelope, and pyrenoid tubules of the chloroplast. Activity was also localized to the Golgi apparatus and its associated vesicles. Additionally, LPA acyltransferase activity was found associated with the outer mitochondrial membranes. The cytochemical data from this study confirm the biochemical data obtained using purified chloroplast membranes (Jelsema et al., 1982) and establishes the presence of these glycerolipid-synthesizing enzymes in the photosynthetic membranes of the chloroplast. These findings support the earlier reports of the presence and activity of lipid-synthesizing enzymes in the chloroplast, and also is in agreement with the postulated role of the pyrenoid tubules in the synthesis of the thylakoid membranes. This report differs in that these lipid-synthesizing enzymes have been localized to the chloroplast photosynthetic membranes themselves as well as exhibiting significant levels of activity for both enzymes in the Golgi apparatus. During light-induced chloroplast biogenesis in the yellow mutant of C. reinhardtii (y-1), the photosynthetic membranes appear to be the primary site of acyltransferase activity, suggesting that in situ synthesis of the membrane lipids during this period of rapid membrane formation is the primary mode for the synthesis of the thylakoid lipids. That these intrinsic thylakoid enzyme activities are not exclusively a function of the growth phase of the cell, but are found in mature chloroplast of the 137+ cells as well, further supports the conclusion that the photosynthetic membranes of the chloroplast have the capacity for synthesis of their own membrane lipids.
我们已经通过细胞化学方法定位了莱茵衣藻中酰基转移酶的活性。利用生物化学优化的反应条件（Jelsema等人，1982年）对3-磷酸甘油（G3P）酰基转移酶和溶血磷脂酸（LPA）酰基转移酶的活性进行了细胞化学分析。细胞化学分析清楚地表明，在野生型细胞（137+）和y-1突变体中，这两种酶都存在于叶绿体的光合膜、包膜和类囊体小管中。活性也定位于高尔基体及其相关的囊泡。此外，发现LPA酰基转移酶活性与线粒体外膜相关。这项研究的细胞化学数据证实了使用纯化的叶绿体膜获得的生物化学数据（Jelsema等人，1982年），并确定了这些甘油脂合成酶在叶绿体光合膜中的存在。这些发现支持了早期关于叶绿体中脂质合成酶的存在和活性的报道，也与类囊体小管在类囊体膜合成中的假定作用一致。本报告的不同之处在于，这些脂质合成酶已定位到叶绿体光合膜本身，并且在高尔基体中这两种酶都表现出显著的活性水平。在莱茵衣藻黄色突变体（y-1）的光诱导叶绿体生物发生过程中，光合膜似乎是酰基转移酶活性的主要部位，这表明在快速膜形成期间膜脂的原位合成是类囊体脂合成的主要模式。这些内在的类囊体酶活性不仅是细胞生长阶段的函数，而且在137+细胞的成熟叶绿体中也能发现，这进一步支持了叶绿体光合膜具有合成自身膜脂能力的结论。
