Bertello Laura E, Alves Maria Júlia M, Colli Walter, de Lederkremer Rosa M
CIHIDECAR, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, 1428 Buenos Aires, Argentina.
Mol Biochem Parasitol. 2004 Jan;133(1):71-80. doi: 10.1016/j.molbiopara.2003.09.007.
The major free glycoinositolphospholipids and protein-linked glycoinositolphospholipids in Trypanosoma cruzi contain ceramide as the lipid moiety. Ceramide was not found in mammalian glycosylphosphatidylinositol (GPI)-anchors. An alkylglycerol, either as a lyso species or acylated has been also found in T. cruzi anchors. However, unlike African trypanosomes, no diacylglycerol was detected in the GPI-anchors. Using a membrane preparation from epimastigotes upon labelling with UDP[3H]GlcNAc we identified [3H]GlcNAcPI as the first step of GPI biosynthesis. Both, alkylacylglycerol (major) and diacylglycerol are constituents of the lipid. Although inositolphosphoceramide is the main inositolphospholipid in epimastigotes, it does not incorporate GlcNAc. The de-N-acetylation step afforded [3H]GlcN(alkylacylglycerol)PI and we also detected the [3H]GlcN(lysoacyl)PI. A new metabolite, phosphoGlcN(lysoacyl)PI, which was formed on long incorporation times, was characterized by chemical and enzymatic degradations. Several [3H]-Man labelled GPI precursors were obtained by in vitro GDP[3H]-Man labelling in the presence of UDPGlcNAc. All of them were sensitive to PI-PLC and to saponification conditions, thus, supporting a glycerolipid structure.
克氏锥虫中的主要游离糖肌醇磷脂和蛋白连接糖肌醇磷脂含有神经酰胺作为脂质部分。在哺乳动物糖基磷脂酰肌醇（GPI）锚中未发现神经酰胺。在克氏锥虫的锚中还发现了一种烷基甘油，其以溶血形式或酰化形式存在。然而，与非洲锥虫不同，在GPI锚中未检测到二酰甘油。在用UDP[3H]GlcNAc标记后，使用来自前鞭毛体的膜制剂，我们确定[3H]GlcNAcPI是GPI生物合成的第一步。烷基酰基甘油（主要）和二酰甘油都是脂质的成分。虽然肌醇磷酸神经酰胺是前鞭毛体中的主要肌醇磷脂，但它不掺入GlcNAc。脱N - 乙酰化步骤产生了[3H]GlcN（烷基酰基甘油）PI，我们还检测到了[3H]GlcN（溶血酰基）PI。通过化学和酶促降解对一种新的代谢物磷酸GlcN（溶血酰基）PI进行了表征，该代谢物是在长时间掺入后形成的。通过在UDPGlcNAc存在下进行体外GDP[3H] - Man标记获得了几种[3H] - Man标记的GPI前体。它们都对PI - PLC和皂化条件敏感，因此支持甘油脂质结构。
