Lohia A, Hait N C, Majumder A L
Department of Biochemistry, Bose Institute Calcutta, India.
Mol Biochem Parasitol. 1999 Jan 5;98(1):67-79. doi: 10.1016/s0166-6851(98)00147-9.
L-myo-Inositol 1-phosphate synthase (I-1-P synthase) catalyses the primary reaction for the synthesis of inositol in a variety of prokaryotes, eukaryotes and in the chloroplasts of algae and higher plants. Inositol is a precursor of essential macromolecules like membrane phospholipids, GPI anchor proteins and lipophosphoglycans, which play a determinant role in the pathogenesis of protozoan parasites such as Leishmania and Entamoeba. However, there is no report of I-1-P synthase or its gene from these organisms. The gene INO1 coding for this enzyme was first cloned from Saccharomyces cerevisiae and subsequently from several plants. Using molecular cloning techniques we have isolated and characterised the INO1 gene coding for the enzyme I-1-P synthase from Entamoeba histolytica. Simultaneously, we have purified and characterised the native enzyme from E. histolytica trophozoites and the cloned gene product from Escherichia coli. The gene product and the purified enzyme were both shown to be recognised by a heterologous anti-I-1-P synthase antibody from the phytoflagellate Euglena gracilis. Phylogenetic analysis of I-1-P synthase sequences from different eukaryotes suggest that it is highly conserved across species and the origin of this enzyme precedes the evolutionary divergence of modern eukaryotes.
L-肌醇-1-磷酸合酶（I-1-P合酶）催化多种原核生物、真核生物以及藻类和高等植物叶绿体中肌醇合成的初级反应。肌醇是膜磷脂、糖基磷脂酰肌醇锚定蛋白和脂磷壁酸等必需大分子的前体，这些大分子在利什曼原虫和溶组织内阿米巴等原生动物寄生虫的发病机制中起决定性作用。然而，尚无关于这些生物体中I-1-P合酶或其基因的报道。编码该酶的INO1基因首先从酿酒酵母中克隆出来，随后又从几种植物中克隆得到。利用分子克隆技术，我们从溶组织内阿米巴中分离并鉴定了编码I-1-P合酶的INO1基因。同时，我们从溶组织内阿米巴滋养体中纯化并鉴定了天然酶以及从大肠杆菌中获得的克隆基因产物。来自植物鞭毛虫纤细裸藻的异源抗I-1-P合酶抗体能够识别基因产物和纯化后的酶。对不同真核生物I-1-P合酶序列的系统发育分析表明，该酶在物种间高度保守，其起源早于现代真核生物的进化分歧。
