Prioli R P, Rosenberg I, Pereira M E
Proc Natl Acad Sci U S A. 1987 May;84(10):3097-101. doi: 10.1073/pnas.84.10.3097.
Plasma of normal human individuals was shown to contain an inhibitor of Trypanosoma cruzi neuraminidase (NAase; acylneuraminyl hydrolase, sialidase, EC 3.2.1.18). The inhibitor has been purified to homogeneity by PEG precipitation, CM Affi-Gel Blue Sepharose chromatography, and gel filtration. The purified preparation inhibits T. cruzi NAase at a concentration as low as 10(-9) M and has no effect at concentrations at least 100 times higher on any of the other NAases tested, including those from influenza virus, the closely related trypanosome Trypanosoma rangeli, and mammalian NAases. The inhibitor is unique in that it prevents T. cruzi desialylation of intact mammalian cells but does not prevent desialylation of soluble glycoconjugates. In addition, the isolated material is effective in inhibiting the T. cruzi NAase whether the enzyme is on the parasite outer membrane or in solution. Molecular characterization indicates that the inhibitor is a glycoprotein with a Mr of 246,000 +/- 20,000 composed of subunits of Mr 28,000 +/- 2000. Its plasma concentration is at least 60 micrograms/ml. The mechanism of action has not been fully elucidated, but it appears to be noncompetitive. Attempts to match the isolated NAase inhibitor with known plasma glycoproteins have not been successful. In view of this and of the specificity of the inhibitor for T. cruzi, we have named the inhibitor "cruzin." This finding suggests a different approach in investigating the role that NAase plays in host-parasite interaction.
正常人类个体的血浆被证明含有克氏锥虫神经氨酸酶（NAase；酰基神经氨酸水解酶、唾液酸酶，EC 3.2.1.18）的抑制剂。通过聚乙二醇沉淀、CM Affi - Gel Blue琼脂糖凝胶层析和凝胶过滤，该抑制剂已被纯化至同质。纯化后的制剂在低至10^(-9) M的浓度下就能抑制克氏锥虫NAase，而在至少高100倍的浓度下，对任何其他测试的NAase均无作用，包括来自流感病毒、密切相关的锥虫罗氏锥虫以及哺乳动物NAase。该抑制剂的独特之处在于，它能阻止克氏锥虫对完整哺乳动物细胞的去唾液酸化，但不能阻止可溶性糖缀合物的去唾液酸化。此外，无论该酶是在寄生虫外膜上还是在溶液中，分离出的物质都能有效抑制克氏锥虫NAase。分子特征表明，该抑制剂是一种糖蛋白，相对分子质量为246,000 ± 20,000，由相对分子质量为28,000 ± 2000的亚基组成。其血浆浓度至少为60微克/毫升。作用机制尚未完全阐明，但似乎是非竞争性的。将分离出的NAase抑制剂与已知血浆糖蛋白进行匹配的尝试尚未成功。鉴于此以及该抑制剂对克氏锥虫的特异性，我们将该抑制剂命名为“cruzin”。这一发现为研究NAase在宿主 - 寄生虫相互作用中所起的作用提供了一种不同的方法。
