Samad A, Licht B, Stalmach M E, Mellors A
Department of Biomedical Sciences, University of Guelph, Ontario, Canada.
Mol Biochem Parasitol. 1988 Jun;29(2-3):159-69. doi: 10.1016/0166-6851(88)90071-0.
African trypanosomes (Trypanosoma brucei brucei) rapidly metabolize exogenous 1-acyl-lysophospholipids by at least two routes: (1) hydrolysis by a phospholipase A1; (2) acylation by an acyl-CoA-dependent acyltransferase. In contrast to lysophospholipids, exogenous phospholipids are not rapidly metabolized by T. brucei. The acyltransferase (EC 2.3.1.23) converts exogenous 1-acyl lysophosphatidylcholine and exogenous acyl-CoA to phosphatidylcholine and CoA-SH. It is a membrane-bound enzyme and shows maximal activity within the first 2 min of exposure of trypanosomes to the exogenous substrates. The acyltransferase specificity for lysophospholipids is lysophosphatidylcholine greater than lysophosphatidylinositol greater than lysophosphatidylethanolamine greater than lysophosphatidate. Phosphatidylcholine enhances the enzyme activity towards lysophosphatidylethanolamine and lysophosphatidic acid. The preference for CoA acyl thioesters is oleoyl greater than palmitoyl greater than myristoyl greater than stearoyl greater than arachidonoyl, and this specificity distinguishes the protozoan enzyme from those of cells of mammalian hosts, which are specific for arachidonoyl-CoA. When the acyltransferase converts exogenous lysophosphatidylethanolamine to phosphatidylethanolamine, the latter is rapidly methylated to form dimethylphosphatidylethanolamine. There is also rapid hydrolysis of exogenous oleoyl-CoA by a thioester hydrolase in living trypanosomes, to yield free oleate and CoA-SH.
非洲锥虫（布氏锥虫布氏亚种）通过至少两条途径快速代谢外源性1-酰基溶血磷脂：（1）由磷脂酶A1水解；（2）由酰基辅酶A依赖性酰基转移酶进行酰化。与溶血磷脂不同，外源性磷脂不会被布氏锥虫快速代谢。酰基转移酶（EC 2.3.1.23）将外源性1-酰基溶血磷脂酰胆碱和外源性酰基辅酶A转化为磷脂酰胆碱和辅酶A-SH。它是一种膜结合酶，在锥虫暴露于外源性底物的前2分钟内表现出最大活性。酰基转移酶对溶血磷脂的特异性为溶血磷脂酰胆碱大于溶血磷脂酰肌醇大于溶血磷脂酰乙醇胺大于溶血磷脂酸。磷脂酰胆碱增强了该酶对溶血磷脂酰乙醇胺和溶血磷脂酸的活性。对辅酶A酰基硫酯的偏好顺序为油酰基大于棕榈酰基大于肉豆蔻酰基大于硬脂酰基大于花生四烯酰基，这种特异性将原生动物酶与哺乳动物宿主细胞的酶区分开来，后者对花生四烯酰基辅酶A具有特异性。当酰基转移酶将外源性溶血磷脂酰乙醇胺转化为磷脂酰乙醇胺时，后者会迅速甲基化形成二甲基磷脂酰乙醇胺。活的锥虫中还存在硫酯水解酶对外源性油酰基辅酶A的快速水解，产生游离油酸和辅酶A-SH。
