Departments of Biochemistry and Genetics, The Connecticut Agricultural Experiment Station, New Haven, Connecticut 06504.
Plant Physiol. 1976 Feb;57(2):334-8. doi: 10.1104/pp.57.2.334.
A three-phase discontinuous sucrose gradient yielded two fractions of chloroplast envelope membranes from spinach (Spinacia oleracea L.), sunflower (Helianthus annuus L.), and maize (Zea mays L., mesophyll and undifferentiated chloroplasts). These species were selected to represent plants with fast photorespiration and slow net photosynthesis, fast photorespiration yet fast net photosynthesis, and slow photorespiration and fast net photosynthesis, respectively. Buoyant densities were 1.08 and 1.11 g cm(-3). The light fraction contained primarily single (incomplete) membrane vesicles and the heavy fraction double (complete) ones. Enzymic, chemical, and electron microscopic examination of the complete envelope membranes showed a lack of microbial, microsomal, mitochondrial, and lamellar membrane contamination as well as stromal contamination. Envelope membranes for all species examined were found to contain 2 to 4% of the total chloroplast protein and yields of about 0.2 to 0.4 mg of protein were obtained from 40 g leaves. An Mg(2+)-dependent nonlatent ATPase, a marker enzyme for chloroplast envelope membranes, had the following activities (mumoles of phosphate released/hr(-1) mg protein(-1)): spinach, 77; sunflower, 163; old maize, 126; and young maize, 87. Bicarbonate transport was directly correlated with levels of ATPase activity in spinach and sunflower envelope membranes. Transport of HCO(3) (-) with sunflower envelope membranes approached that of young maize.
从菠菜（Spinacia oleracea L.）、向日葵（Helianthus annuus L.）和玉米（Zea mays L.，叶肉和未分化的叶绿体）中，通过三相不连续蔗糖梯度得到叶绿体被膜的两个级分。选择这些物种是为了分别代表具有快速光呼吸和慢速净光合作用、快速光呼吸但快速净光合作用以及慢速光呼吸和快速净光合作用的植物。浮力密度分别为 1.08 和 1.11 g cm(-3)。轻级分主要含有单（不完整）膜小泡，而重组分则含有双（完整）膜小泡。对完整被膜的酶学、化学和电子显微镜检查表明，不存在微生物、微粒体、线粒体和片层膜污染以及基质污染。检查的所有物种的被膜都发现含有 2%至 4%的总叶绿体蛋白，从 40 g 叶片中获得约 0.2 至 0.4 mg 的蛋白产量。Mg(2+)-依赖性非潜伏 ATP 酶是叶绿体被膜的标记酶，其活性（每小时每毫克蛋白释放的磷酸盐摩尔数）如下：菠菜，77；向日葵，163；老玉米，126；和幼玉米，87。碳酸根（HCO(3) (-)）的转运与菠菜和向日葵被膜中的 ATP 酶活性水平直接相关。用向日葵被膜进行 HCO(3) (-)的转运接近幼玉米的水平。
