Beta 1-3-N-acetylglucosaminyltransferase in human leukocytes: properties and role in regulating neolacto glycosphingolipid biosynthesis.
Beta 1-3-N-acetylglucosaminyltransferase in human leukocytes: properties and role in regulating neolacto glycosphingolipid biosynthesis.
复制标题
人类白细胞中的β 1-3-N-乙酰氨基葡萄糖转移酶：特性和在调节新乳糖鞘脂生物合成中的作用。
DOI：
10.1006/abbi.1993.1263
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发表时间：
1993
影响因子：
3.9
通讯作者：
Macher,BA
中科院分区：
文献类型：
--
作者：
Stults,CL;Macher,BA
在人类白细胞亚类中，新乳糖中性鞘糖脂的表达存在明确的差异。成熟的骨髓细胞表达几种类型的这些化合物，而成熟的淋巴样细胞缺乏这些化合物。其生物化学基础尚不清楚。因此，进行了酶研究，以确定不同类别的白细胞（以细胞系为代表）是否含有β1-3-N-乙酰葡糖胺转移酶活性（EC 2.4.1.149，β1-3GlcNAcT（i））。该酶通过催化以下两个反应参与鞘糖脂中2型链的合成：（i）Galβ1-4Glcβ1-1Cer（乳糖神经酰胺，LacCer）+ UDP-GlcNAc → GlcNAcβ1-3Galβ1-4Glcβ1-1Cer（乳糖三己糖神经酰胺）和（ii）Galβ1-4GlcNAcβ1-3Galβ1-4Glcβ1-1Cer（新乳糖四己糖神经酰胺）+ UDP-GlcNAc → GlcNAc β 1 - 3Gal β 1 - 4GlcNAc β 1 - 3Gal β 1 - 4Glcβ1-1Cer。第一个反应可能是人类白细胞中新乳糖结构生物合成途径的关键步骤。因此，用LacCer分析了代表不同成熟阶段的髓系和淋巴系的几种细胞系的提取物中是否存在β1-3GlcNAcT（i）活性。我们的研究结果表明，髓样细胞含有这种起始β1-3GlcNAcT（i）活性，而淋巴样细胞不含。这与我们的薄层色谱免疫染色结果一致，该结果显示所有髓样细胞系均表达中性新乳糖鞘糖脂，而淋巴样细胞不表达。我们的研究结果表明，启动活性的存在下，只有在骨髓细胞是一个调节因子的中性新乳糖鞘糖脂在人类白细胞的表达。我们还通过使用新乳四糖神经酰胺作为受体，测试了髓样和淋巴样细胞系是否存在延长β1-3GlcNAcT（i）活性（上述反应（ii））。我们的研究结果表明，延长活动的所有骨髓和淋巴细胞系测试。启动（骨髓）和延长（骨髓和淋巴）活动的区别有几个特点：金属离子活化，最佳pH值，和动力学常数。总之，我们的研究结果表明，在人类白细胞中存在两种β1-3GlcNAcT（i）活性：一种催化初始反应，仅在髓系中发现，另一种催化延伸反应，在髓系和淋巴细胞中发现。
There are well-established differences in the expression of neolacto neutral glycosphingolipids among human leukocyte subclasses. Mature myeloid cells express several types of these compounds, whereas mature lymphoid cells are deficient in such compounds. The biochemical basis for this is unknown. Therefore, enzyme studies were done to determine whether different classes of leukocytes (represented by cell lines) contained β1-3-N-acetylglucosaminyltransferase activity (EC 2.4.1.149, β1-3GlcNAcT(i)). This enzyme participates in the synthesis of Type 2 chains in glycosphingolipids by catalyzing the following two reactions: (i) Galβ1-4Glcβ1-1Cer (lactosylceramide, LacCer) + UDP-GlcNAc → GlcNAcβ1-3Galβ1-4Glcβ1-1Cer (lactotriaosylceramide) and (ii) Galβ1-4GlcNAcβ1-3Galβ1-4Glcβ1-1Cer (neolactotetraosylceramide) + UDP-GlcNAc → GlcNAcβ1-3Galβ1-4GlcNAcβ1-3Galβ1-4Glcβ1-1Cer. The first reaction may be the key step in the biosynthetic pathway of neolacto structures in human leukocytes. Therefore, extracts from several cell lines representative of both myeloid and lymphoid lineages, at varied stages of maturity, were assayed with LacCer for the presence of β1-3GlcNAcT(i) activity. Our results indicate that myeloid cells contain this initiating β1-3GlcNAcT(i) activity, whereas lymphoid cells do not. This is consistent with our thin-layer chromatography immunostain results which show that all myeloid cell lines express neutral neolacto glycosphingolipids and lymphoid cells do not. Our findings suggest that the presence of the initiating activity only in myeloid cells is a regulatory factor in the expression of neutral neolacto glycosphingolipids in human leukocytes. We also tested both myeloid and lymphoid cell lines for the presence of elongating β1-3GlcNAcT(i) activity (reaction (ii) above) by using neolactotetraosylceramide as an acceptor. Our results show that an elongating activity is expressed by all myeloid and lymphoid cell lines tested. Initiating (myeloid) and elongating (myeloid and lymphoid) activities were distinguished by several characteristics: metal ion activation, pH optimum, and kinetic constants. In conclusion, our results indicate the presence of two β1-3GlcNAcT(i) activities in human leukocytes: one that catalyzes the initial reaction and is found only in the myeloid lineage and one that catalyzes the elongating reaction and is found in both myeloid and lymphoid cells.