When [2-3H]glycerol was supplied to developing maize-leaf laminae, label entered 3-sn-phosphatidycholine at a linear rate essentially from zero time, whereas other lipids were labelled at accelerating rates. On transfer of laminae from [3H]glycerol to unlabelled glycerol, radioactivity was rapidly lost from 3-sn-phosphatidylcholine and accumulated in other lipids, principally monogalactosyl diacyglycerol. 2. Degradation of these lipids showed that 3H was present only in the glycerol moiety of the lipids. 3. In double-labelling pulse-chase experiments with [14C]acetate, which labelled essentially only fatty acids and [3H]glycerol similar amounts of 14C and 3H radioactivity were lost from 3-sn-phosphatidylcholine and accumulated by monogalactosyl diacylglycerol. 4. The different molecular species of both lipids isolated from laminae during a double-labelled pulse-chase study were separated by argentation t.l.c., and the changes in the amount of radioactivity and the 14C/3H ratio in different species were compared. The greatest loss of radioactivity during the period in unlabelled substrates occurred from the 3-sn-phosphatidylcholine species containing oleate and from the dilinoleate species, and radioactivity accumulated by monogalactosyl diacyglycerol was mainly in the dilinolenate species. However, despite the considerable change in the radioactivity in these species during the chase, the 14C/3H ratio in each of them remained relatively unchanged. 5. It is proposed that 3-sn-phosphatidylcholine in the developing leaf may serve as a donor or linoleate-containing diacyl-glycerols which are incorporated into other lipids, principally monogalactosyl diacylglycerol.
摘要
当向发育中的玉米叶片供应[2-³H]甘油时，放射性标记基本上从零时起以线性速率进入3- sn -磷脂酰胆碱，而其他脂质的标记速率则不断加快。当叶片从[³H]甘油转移至未标记的甘油时，3- sn -磷脂酰胆碱中的放射性迅速丧失，并在其他脂质中积累，主要是单半乳糖基二酰基甘油。2. 这些脂质的降解表明³H仅存在于脂质的甘油部分。3. 在使用[¹⁴C]乙酸盐进行的双标记脉冲追踪实验中，[¹⁴C]乙酸盐基本上只标记脂肪酸，[³H]甘油与之类似，3- sn -磷脂酰胆碱中丧失的¹⁴C和³H放射性数量相近，并在单半乳糖基二酰基甘油中积累。4. 在双标记脉冲追踪研究期间，从叶片中分离出的两种脂质的不同分子种类通过银染薄层层析法进行分离，并比较不同种类中放射性数量和¹⁴C/³H比率的变化。在未标记底物的时期内，放射性丧失最多的是含有油酸的3- sn -磷脂酰胆碱种类和二亚油酸种类，单半乳糖基二酰基甘油积累的放射性主要存在于二亚麻酸种类中。然而，尽管在追踪过程中这些种类的放射性发生了相当大的变化，但它们各自的¹⁴C/³H比率仍相对保持不变。5. 有人提出，发育叶片中的3- sn -磷脂酰胆碱可能作为含亚油酸的二酰基甘油的供体，这些二酰基甘油被并入其他脂质中，主要是单半乳糖基二酰基甘油。
