Beach D H, Holz G G, Singh B N, Lindmark D G
Department of Microbiology and Immunology, SUNY Health Science Center, Syracuse, NY.
Mol Biochem Parasitol. 1990 Jan 15;38(2):175-90. doi: 10.1016/0166-6851(90)90021-d.
Trichomonas vaginalis and Tritrichomonas foetus grown in a fetal calf serum-based culture medium, contained as major lipids (i.e., greater than 10% of total) cholesterol, phosphatidylethanolamine and phosphatidylcholine. T. vaginalis also contained sphingomyelin and T. foetus glycophosphosphingolipids. The culture medium contained (greater than 10%) cholesterol, phosphatidylethanolamine, phosphatidylcholine, sphingomyelin and lysophosphatidylcholine. The fatty acyl groups of these major lipids of the trichomonads and the culture medium were similar. Those present in amounts greater than 5% of the total fatty acyl groups for a given lipid were myristic, palmitic, hexadecaenoic, stearic, oleic, linoleic, arachidonic and docosahexaenoic. When the trichomonads were exposed to radiolabeled lipids and lipid precursors, [14C]-labeled acetate and potential acetate precursors (glucose, threonine) were poorly incorporated and failed to label the fatty acyl groups of the trichomonad lipids. [14C]-labeled, C12-C22 saturated and unsaturated fatty acids were incorporated, unaltered, into phosphoglycerides and sphingolipids (sphingomyelin and glycophosphosphingolipids), but not into cholesteryl esters or triacylglycerols. Phosphoglycerides were preferentially labeled with unsaturated fatty acids and sphingolipids with saturated ones. This information inferred that the trichomonads: 1) were unable to biosynthesize fatty acids de novo, 2) took up unesterified fatty acids from the culture medium and used them in phosphoglyceride and sphingolipid biosynthesis and/or turnover, 4) did not use unesterified fatty acids in the biosynthesis or turnover of cholesteryl esters or triacylglycerols. Phosphatidylcholine and phosphatidylethanolamine, with [14C]labeled fatty acyl groups, and sphingomyelin, with 14C-labeled choline, were incorporated by the trichomonads. The phospholipids strongly labeled phosphoglycerides and sphingolipids, but not triacylglycerols, while the radioactivity of sphingomyelin [14C]choline remained associated solely with trichomonad sphingomyelin. Triacylglycerol, with 14C-labeled fatty acyl groups, was also incorporated, and labeled phosphoglycerides and sphingolipids. The results of those experiments suggested that trichomonads: (1) could take up culture medium phospholipids and triacylglycerols; (2) actively deacylated and reacylated phospholipids, but not triacylglycerols; (3) hydrolyzed exogenous triacylglycerols and used their fatty acyl groups for phospholipid acylations. Radiolabeled acetate, mevalonate and squalene were not incorporated into trichomonad cholesterol or cholesteryl esters. [14C]Cholesterol was incorporated unaltered, but was not esterified.(ABSTRACT TRUNCATED AT 400 WORDS)
在基于胎牛血清的培养基中培养的阴道毛滴虫和胎儿三毛滴虫，其主要脂质（即占总量的10%以上）包括胆固醇、磷脂酰乙醇胺和磷脂酰胆碱。阴道毛滴虫还含有鞘磷脂，胎儿三毛滴虫含有糖磷脂酰鞘脂。培养基中含有（超过10%）胆固醇、磷脂酰乙醇胺、磷脂酰胆碱、鞘磷脂和溶血磷脂酰胆碱。这些滴虫和培养基的主要脂质的脂肪酰基相似。对于给定脂质，占总脂肪酰基5%以上的脂肪酸有肉豆蔻酸、棕榈酸、十六碳烯酸、硬脂酸、油酸、亚油酸、花生四烯酸和二十二碳六烯酸。当滴虫暴露于放射性标记的脂质和脂质前体时，[14C]标记的乙酸盐和潜在的乙酸盐前体（葡萄糖、苏氨酸）掺入量很少，且未能标记滴虫脂质的脂肪酰基。[14C]标记的C12 - C22饱和及不饱和脂肪酸未发生改变地掺入磷脂酰甘油和鞘脂（鞘磷脂和糖磷脂酰鞘脂）中，但未掺入胆固醇酯或三酰甘油中。磷脂酰甘油优先被不饱和脂肪酸标记，鞘脂则被饱和脂肪酸标记。这些信息表明滴虫：1）无法从头生物合成脂肪酸；2）从培养基中摄取未酯化的脂肪酸，并将其用于磷脂酰甘油和鞘脂的生物合成及/或周转；4）在胆固醇酯或三酰甘油的生物合成或周转中不使用未酯化的脂肪酸。带有[14C]标记脂肪酰基的磷脂酰胆碱和磷脂酰乙醇胺，以及带有14C标记胆碱的鞘磷脂被滴虫掺入。这些磷脂强烈标记磷脂酰甘油和鞘脂，但不标记三酰甘油，而鞘磷脂[14C]胆碱的放射性仅与滴虫鞘磷脂相关。带有14C标记脂肪酰基的三酰甘油也被掺入，并标记磷脂酰甘油和鞘脂。这些实验结果表明滴虫：（1）可以摄取培养基中的磷脂和三酰甘油；（2）积极地对磷脂进行去酰化和再酰化，但不对三酰甘油进行此操作；（3）水解外源性三酰甘油并将其脂肪酰基用于磷脂酰化。放射性标记的乙酸盐、甲羟戊酸和角鲨烯未掺入滴虫胆固醇或胆固醇酯中。[14C]胆固醇未发生改变地被掺入，但未被酯化。（摘要截选至400字）
