Villalobo Eduardo, Wender Nomy, Mirelman David
Department of Biological Chemistry, Weizmann Institute of Science, 76100 Rehovot, Israel.
Exp Parasitol. 2005 Jul;110(3):298-302. doi: 10.1016/j.exppara.2005.03.022.
In cells, the alpha-anomers of aldoses are the preferred metabolizable substrates, while beta-anomers of aldoses play their role in glycan structure. In the cytoplasm, alpha- and beta-anomers of aldoses interconvert through the enzyme termed aldose 1-epimerase or mutarotase (EC 5.1.3.3). We have identified a mutarotase gene in Entamoeba histolytica, the causative agent of non-bacterial dysentery in humans. Cloning and characterization of this gene in two strains of the parasite (HM-1:IMSS and Rahman) that differ in their pathogenicity, revealed that the sequence is identical in both strains. A recombinant E. histolytica mutarotase was produced as well as specific antibodies that recognized a 38 kDa protein in trophozoite lysates of both strains. Mutarotase activity was observed with the recombinant protein as well as in lysates of both HM-1:IMSS and Rahman, the former exhibiting a slightly higher mutarotase activity. Finally, we have shown by complementation that overexpression of the E. histolytica mutarotase in a mutarotase defective Escherichia coli strain restores the ability of these bacteria to grow in minimal medium with phenyl-beta-galactopyranoside as the sole carbon source.
在细胞中，醛糖的α-异头物是首选的可代谢底物，而醛糖的β-异头物则在聚糖结构中发挥作用。在细胞质中，醛糖的α-和β-异头物通过称为醛糖1-差向异构酶或变旋酶（EC 5.1.3.3）的酶相互转化。我们在溶组织内阿米巴中鉴定出一个变旋酶基因，溶组织内阿米巴是人类非细菌性痢疾的病原体。对该寄生虫的两个致病性不同的菌株（HM-1:IMSS和拉赫曼）中的这个基因进行克隆和表征，结果显示这两个菌株中的序列是相同的。制备了重组溶组织内阿米巴变旋酶以及能识别这两个菌株滋养体裂解物中一种38 kDa蛋白质的特异性抗体。在重组蛋白以及HM-1:IMSS和拉赫曼菌株的裂解物中均观察到变旋酶活性，前者的变旋酶活性略高。最后，我们通过互补实验表明，在变旋酶缺陷的大肠杆菌菌株中过表达溶组织内阿米巴变旋酶可恢复这些细菌在以苯基-β-吡喃半乳糖苷作为唯一碳源的基本培养基中生长的能力。
