Roughan P G
Lipids. 1975 Oct;10(10):609-14. doi: 10.1007/BF02532725.
Kinetics of radiocarbon inforporation into the phyosphatidyl choline of pumpkin leaf fed 1(-14)C-acetate at low light intensity were strongly suggestive of lipid bound fatty acids acting as substrates for desaturase enzymes. After pulse labeling in direct sunlight with the same precursor, phosphatidyl choline and phosphatidyl glycerol contained up to 90% of total glycerolipid radiocarbon at the shortest sampling times. Subsequent loss of radiocarbon from phyosphatidyl choline and a corresponding gain in other glycerolipids is taken to indicate a net flow of long chain fatty acids through phosphatidyl choline and into other lipids. It is proposed that there may be 2 separate synthetases in leaf tissue, one producing oleic and the other palmitic acids as their end products. Oleic acid is transferred almost exclusively to phosphatidyl choline where it is further desaturated to linoleic and linolenic acids before being made available for the biosynthesis of other lipids. Palmitic acid is transferred mainly to phosphatidyl glycerol, where it is desaturated to trans-delta3-hexadecenoic acid.
在低光照强度下用1(-14)C-乙酸喂养南瓜叶时，放射性碳掺入磷脂酰胆碱的动力学有力地表明，与脂质结合的脂肪酸充当去饱和酶的底物。在用相同前体在直射阳光下进行脉冲标记后，在最短采样时间时，磷脂酰胆碱和磷脂酰甘油含有高达90%的总甘油脂放射性碳。随后放射性碳从磷脂酰胆碱中损失，而在其他甘油脂中相应增加，这被认为表明长链脂肪酸通过磷脂酰胆碱并流入其他脂质的净流动。有人提出，叶组织中可能存在两种独立的合成酶，一种产生油酸作为终产物，另一种产生棕榈酸作为终产物。油酸几乎完全转移到磷脂酰胆碱中，在那里它进一步去饱和为亚油酸和亚麻酸，然后才用于其他脂质的生物合成。棕榈酸主要转移到磷脂酰甘油中，在那里它去饱和为反式-δ3-十六碳烯酸。
