Expression cloning of a human GT3 synthase. GD3 AND GT3 are synthesized by a single enzyme.
Expression cloning of a human GT3 synthase. GD3 AND GT3 are synthesized by a single enzyme.
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DOI：
10.1074/jbc.271.7.3684
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发表时间：
1996-02
期刊：
影响因子：
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通讯作者：
J. Nakayama;M. Fukuda;Y. Hirabayashi;A. Kanamori;K. Sasaki;T. Nishi;M. Fukuda
中科院分区：
文献类型：
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作者：
J. Nakayama;M. Fukuda;Y. Hirabayashi;A. Kanamori;K. Sasaki;T. Nishi;M. Fukuda
C系列的神经节苷脂如GT 3是聚唾液酸化的鞘糖脂，其合成受发育调节。本文报道了GT 3合成酶的表达cDNA克隆和表征，GT 3合成酶将第二个α-2，8-唾液酸添加到GD 3，NeuNAcalpha 2--> 8 NeuNAcalpha 2--> 3Galbeta 1-->4Glc-->Cer，从而形成GT 3，NeuNAcalpha 2--> 8 NeuNAcalpha 2--> 8 NeuNAc alpha 2--> 3Galbeta 1--> 4Glc-->Cer。出乎意料的是，发现克隆的cDNA与编码GD 3合酶的cDNA相同。因此，新鉴定的酶被命名为GD 3/GT3合酶（GD 3/GT3 ST）。当GM 3（NeuNAcalpha 2-> 3Galbeta 1->4Glc->Cer）作为受体孵育时，GD 3/GT3 ST最有效地合成GT3，表明GD 3/GT3 ST是一种多聚唾液酸转移酶，可以通过α-2，8键将多于一个唾液酸残基转移到神经节苷脂。此外，GD 3与GD 3/GT 3ST的较长时间的孵育产生了显著量的GT 3和更高的聚唾液酸神经节苷脂。在表达GD 3/GT3 ST的各种细胞系中，仅在GD 3/GT3 mRNA的量足够高的细胞系中检测到包括GT3的较高的聚唾液酸神经节苷脂。GD 3/GT3 ST mRNA在人体组织中的表达高度局限于胎儿和成人脑。GD 3/GT3 ST基因定位于12号染色体p12区。综上所述，这些结果表明，C系列聚唾液酸神经节苷脂是由神经节苷脂特异性聚唾液酸转移酶GD 3/GT3 ST合成的，该酶在神经组织中特异性表达。
Gangliosides of the C series such as GT3 are polysialylated glycosphingolipids whose synthesis is developmentally regulated. Here we report the expression cDNA cloning and characterization of GT3 synthase that adds the second alpha-2,8-sialic acid to GD3, NeuNAcalpha2-->8NeuNAcalpha2-->3Galbeta1-->4Glc-->Cer, thus forming GT3, NeuNAcalpha2-->8NeuNAcalpha2-->8NeuNAc alpha2-->3Galbeta1--> 4Glc-->Cer. Unexpectedly, the cloned cDNA was found to be identical to the cDNA that encodes GD3 synthase. The newly identified enzyme was therefore named GD3/GT3 synthase (GD3/GT3ST). GD3/GT3ST synthesized GT3 most efficiently when GM3, NeuNAcalpha2-->3Galbeta1-->4Glc-->Cer, was incubated as an acceptor, indicating that GD3/GT3ST is a polysialyltransferase that can transfer more than one sialic acid residue via alpha-2,8 linkage to gangliosides. Moreover, a longer period of incubation of GD3 with GD3/GT3ST produced a significant amount of GT3 and higher polysialogangliosides. Among various cell lines expressing GD3/GT3ST, higher polysialogangliosides including GT3 were detected only in cell lines where the amount of GD3/GT3 mRNA is sufficiently high. The expression of GD3/GT3ST mRNA among human tissues is highly restricted to fetal and adult brains. The GD3/GT3ST gene was found to be located at chromosome 12, region p12. Taken together, these results indicate that C series polysialogangliosides are synthesized by a ganglioside-specific polysialyltransferase, GD3/GT3ST, that is specifically expressed in neural tissues.