A bloodstream Trypanosoma congolense sialidase could be involved in anemia during experimental trypanosomiasis
A bloodstream Trypanosoma congolense sialidase could be involved in anemia during experimental trypanosomiasis
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DOI：
10.1093/jb/mvg093
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发表时间：
2003-06-01
影响因子：
2.7
通讯作者：
Balogun, EO
中科院分区：
文献类型：
--
作者：
Nok, AJ;Balogun, EO
本文研究了刚果锥虫感染BalbC小鼠后血清中唾液酸（SA）的释放。观察到血清SA水平的逐渐增加，与贫血和寄生虫血症相对应。在最大寄生虫血症时，来自红细胞（RBC）的总SA水平下降约45%。求解多项式揭示了游离血清SA和RBC-SA之间的关联。二次曲线的正根用于预测第7.01天RBC-SA的完全裂解和第6.6天游离血清SA的最大积累。观察到血清唾液酸酶（SD）活性水平稳步上升，红细胞压积（PCV）降低，寄生虫血症增加。注入半乳糖、甲基-β-半乳糖、乳糖、甘露糖或L-阿拉伯糖并通过腹膜内接种刚果锥虫进行攻击的小鼠既不发生贫血，也不分泌高于对照水平的游离SA，即使存在可检测到的SD活性。使用DEAE纤维素从实验感染的BalbC小鼠的肝素化血液中分离血流刚果锥虫寄生虫。用0. 2% Triton-CF 54裂解寄生虫以释放膜结合的SD。SD的活性与寄生虫的数量成正比。该酶经Q-Sepharose和Fetuin琼脂糖柱纯化。来自后一柱的最终活性级分用作部分纯化的SD。该酶的最适pH值为6，在37 ℃时最大活性，需要二价离子Ca ~（2+）和Mg ~（2+）。该酶对NeuAc 5 α 2，3 lac和甲基伞形酮基-Neu 5Ac（4-MU-Neu 5Ac）具有高度特异性，KM值分别为0.34和0.025 mM。它被2，3-二脱氢神经氨酸（Neu 5Ac 2 en）和对硝基苯氧肟酸（pNPO）竞争性抑制，抑制结合常数Ki分别为65和215 μ M。与前环锥虫SD不同，它缺乏转唾液酸酶（TS）活性。分泌的血流刚果锥虫SD和贫血的发展锥虫病的发病机制可能发挥的作用进行了讨论。
The release of Sialic acid (SA) into the serum by Trypanosoma congolense infected BalbC mice was investigated. A progressive increase in the level of serum SA corresponding to anemia and parasitemia was observed. At maximum parasitemia, the level of total SA from the red blood cells (RBC) dropped by about 45%. Solved polynomials revealed an association between free serum SA and RBC-SA. Positive roots of quadratics were used to predict complete cleavage of RBC-SA on day 7.01 and maximum accumulation of free serum SA on day 6.6. A steady rise in the level of serum sialidase (SD) activity and a low packed cell volume (PCV) with an increase in parasitemia were observed. Mice infused with galactose, methyl-beta-gal, lactose, mannose, or L-arabinose and challenged by intraperitoneal inoculation with Trypanosoma congolense neither developed anemia nor secreted free SA above the control level even though there was detectable SD activity. Bloodstream Trypanosoma congolense parasites were isolated using DEAE cellulose from heparinized blood of experimentally infected BalbC mice. The parasites were lysed with 0.2% Triton-CF 54 to release membrane bound SD. The activity of the SD was proportional to the number of parasites. The enzyme was partially purified on Q-Sepharose and Fetuin agarose columns successively. The final active fraction from the latter column was used as the partially purified SD. The enzyme had an optimum pH of 6 and was maximally active at 37degreesC with a requirement for the divalent ions Ca2+ and Mg2+. The enzyme was highly specific for NeuAc5alpha2,3 lac and Methylumbelliferyl-Neu5Ac (4-MU-Neu5Ac) with KM values of 0.34 and 0.025 mM, respectively. It was inhibited competitively by 2,3-didehydroneuraminic acid (Neu5Ac2en) and para-nitro-phenyloxamic acid (pNPO) with inhibition binding constants K-i of 65 and 215 muM, respectively. In deviation from the procyclic trypanosomal SD, it lacked trans-sialidase (TS) activity. The possible role of a secreted bloodstream Trypanosoma congolense SD and the development of anemia in the pathogensesis of trypanosomiasis are discussed.