Beach D H, Holz G G, Singh B N, Lindmark D G
Department of Microbiology and Immunology, SUNY Health Science Center, Syracuse.
Mol Biochem Parasitol. 1991 Jan;44(1):97-108. doi: 10.1016/0166-6851(91)90225-u.
Trichomonas vaginalis and Tritrichomonas foetus grown in a fetal calf serum-based culture medium were exposed to radiolabeled phospholipids and lipid precursors to determine the extent to which these organisms can incorporate complex lipids and/or de novo synthesize their major membrane phosphoglycerides. Phosphatidylethanolamine and phosphatidylcholine were the dominant phospholipids (40-50% of extractable phospholipids), with acidic lipids, phosphatidylinositol, phosphatidylserine, phosphatidylglycerol and O-acylphosphatidylglycerol accounting for the remaining phosphoglycerides. T. vaginalis was rich in sphingomyelin while T. foetus lacks significant amounts of this lipid. Incubation with [32P]orthophosphate resulted in only modest incorporation into extractable phospholipids; the most striking observation being the failure to label choline-containing lipids (phosphatidylcholine, lysophosphatidylcholine and sphingomyelin). Phosphatidylethanolamine was heavily labeled with modest labeling observed in the acidic phosphoglycerides. [U-14C]Glucose failed to label choline-containing lipids in T. foetus but did so in T. vaginalis, with phosphatidylethanolamine again being heavily labeled. Choline, phosphorylcholine, ethanolamine, serine, inositol, glycerol and methionine were incorporated poorly or failed to label the expected phosphoglycerides in either of the trichomonads, demonstrating an impairment in synthesis. Intact phosphoglycerides, labeled in the fatty acyl groups, labeled most phospholipids indicating that turnover of membrane lipids can occur with respect to the acyl component of the phospholipids. Fluorescent probes attached to phosphoglyceride molecules support observations seen with radiolabeled phosphoglycerides. Though trichomonads are able to transacylate phosphoglycerides, it is evident that the trichomonads lack a variety of enzymatic activities necessary for de novo synthesis of complex phosphoglycerides and must rely on environmental sources to supply them.
将生长于基于胎牛血清的培养基中的阴道毛滴虫和胎儿三毛滴虫暴露于放射性标记的磷脂和脂质前体，以确定这些生物体能够整合复合脂质和/或从头合成其主要膜磷酸甘油酯的程度。磷脂酰乙醇胺和磷脂酰胆碱是主要的磷脂（占可提取磷脂的40 - 50%），酸性脂质、磷脂酰肌醇、磷脂酰丝氨酸、磷脂酰甘油和O - 酰基磷脂酰甘油占其余的磷酸甘油酯。阴道毛滴虫富含鞘磷脂，而胎儿三毛滴虫缺乏大量这种脂质。用[32P]正磷酸盐孵育仅导致少量掺入可提取的磷脂中；最显著的观察结果是未能标记含胆碱的脂质（磷脂酰胆碱、溶血磷脂酰胆碱和鞘磷脂）。磷脂酰乙醇胺被大量标记，酸性磷酸甘油酯有少量标记。[U - 14C]葡萄糖未能标记胎儿三毛滴虫中含胆碱的脂质，但能标记阴道毛滴虫中的此类脂质，磷脂酰乙醇胺再次被大量标记。胆碱、磷酸胆碱、乙醇胺、丝氨酸、肌醇、甘油和蛋氨酸掺入不佳或未能标记两种毛滴虫中预期的磷酸甘油酯，表明合成存在缺陷。在脂肪酰基中标记的完整磷酸甘油酯标记了大多数磷脂，表明膜脂质的周转可能发生在磷脂的酰基成分方面。连接到磷酸甘油酯分子上的荧光探针支持了放射性标记的磷酸甘油酯的观察结果。虽然毛滴虫能够进行磷酸甘油酯的转酰基作用，但很明显，毛滴虫缺乏从头合成复合磷酸甘油酯所需的多种酶活性，必须依赖环境来源来供应它们。
