Lawrence S M, Huddleston K A, Pitts L R, Nguyen N, Lee Y C, Vann W F, Coleman T A, Betenbaugh M J
Departments of Chemical Engineering and Biology, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
J Biol Chem. 2000 Jun 9;275(23):17869-77. doi: 10.1074/jbc.M000217200.
Sialic acids participate in many important biological recognition events, yet eukaryotic sialic acid biosynthetic genes are not well characterized. In this study, we have identified a novel human gene based on homology to the Escherichia coli sialic acid synthase gene (neuB). The human gene is ubiquitously expressed and encodes a 40-kDa enzyme. The gene partially restores sialic acid synthase activity in a neuB-negative mutant of E. coli and results in N-acetylneuraminic acid (Neu5Ac) and 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (KDN) production in insect cells upon recombinant baculovirus infection. In vitro the human enzyme uses N-acetylmannosamine 6-phosphate and mannose 6-phosphate as substrates to generate phosphorylated forms of Neu5Ac and KDN, respectively, but exhibits much higher activity toward the Neu5Ac phosphate product.
唾液酸参与许多重要的生物识别事件，然而真核生物唾液酸生物合成基因的特征尚未得到充分研究。在本研究中，我们基于与大肠杆菌唾液酸合酶基因（neuB）的同源性鉴定出一个新的人类基因。该人类基因在全身广泛表达，编码一种40 kDa的酶。该基因能部分恢复大肠杆菌neuB阴性突变体中的唾液酸合酶活性，并在重组杆状病毒感染后使昆虫细胞产生N - 乙酰神经氨酸（Neu5Ac）和2 - 酮 - 3 - 脱氧 - D - 甘油 - D - 半乳糖壬糖酸（KDN）。在体外，该人类酶分别以N - 乙酰甘露糖胺6 - 磷酸和甘露糖6 - 磷酸为底物生成Neu5Ac和KDN的磷酸化形式，但对Neu5Ac磷酸产物表现出更高的活性。
