Miyamoto D, Takashima S, Suzuki T, Nishi T, Sasaki K, Morishita Y, Suzuki Y
Department of Biochemistry, University of Shizuoka, School of Pharmaceutical Science, Japan.
Biochem Biophys Res Commun. 1995 Dec 26;217(3):852-8. doi: 10.1006/bbrc.1995.2850.
A human Gal beta(1-3/1-4)GlcNAc alpha 2,3-sialyltransferase, called ST-4, is a sialyltransferase involved in the in vivo biosynthesis of sialyl Lewis X (NeuNAc alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc) determinant. The ST-4 enzyme could utilize nLc4Cer (Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc beta 1-1'Cer) containing type 2 sugar chain, Lc4Cer (Gal beta 1-3GlcNAc beta 1-3Gal beta 1-4Glc beta 1-1'Cer) containing type 1 sugar chain, Gg4Cer (Gal beta 1-3GalNAc beta 1-3Gal beta 1-4Glc beta 1-1'Cer), and LacCer as glycolipid acceptor substrates, but not other neutral glycolipids (GalCer, GlcCer, Gb3Cer, Gg3Cer, Gb4Cer) and gangliosides (GM1a, GM2, GM3, GD1a, GD1b, and GT1b) as substrates. The order of sialic acid incorporation into glycolipids for the enzyme was nLc4Cer > Gg4Cer > Lc4Cer > LacCer. The apparent Km values of ST-4 for nLc4Cer and Gg4Cer were 0.47 and 2.5 mM, respectively. Thus, the ST-4 could efficiently utilize both nLc4Cer and Gg4Cer as glycolipid acceptor substrates in vitro, suggesting that the substrate specificity of the enzyme may be similar to that of a glycolipid sialyltransferase (SAT-3), which is defined as the enzyme that uses both nLc4Cer and Gg4Cer as glycolipid acceptor substrates.
一种名为ST-4的人源Galβ(1-3/1-4)GlcNAcα2,3-唾液酸转移酶，是一种参与唾液酸化路易斯X（NeuNAcα2-3Galβ1-4(Fucα1-3)GlcNAc）决定簇体内生物合成的唾液酸转移酶。ST-4酶可利用含有2型糖链的nLc4Cer（Galβ1-4GlcNAcβ1-3Galβ1-4Glcβ1-1'Cer）、含有1型糖链的Lc4Cer（Galβ1-3GlcNAcβ1-3Galβ1-4Glcβ1-1'Cer）、Gg4Cer（Galβ1-3GalNAcβ1-3Galβ1-4Glcβ1-1'Cer）和LacCer作为糖脂受体底物，但不能利用其他中性糖脂（GalCer、GlcCer、Gb3Cer、Gg3Cer、Gb4Cer）和神经节苷脂（GM1a、GM2、GM3、GD1a、GD1b和GT1b）作为底物。该酶将唾液酸掺入糖脂的顺序为nLc4Cer > Gg4Cer > Lc4Cer > LacCer。ST-4对nLc4Cer和Gg4Cer的表观Km值分别为0.47和2.5 mM。因此，ST-4在体外可有效利用nLc4Cer和Gg4Cer作为糖脂受体底物，这表明该酶的底物特异性可能与一种糖脂唾液酸转移酶（SAT-3）相似，SAT-3被定义为使用nLc4Cer和Gg4Cer作为糖脂受体底物的酶。
