Cloning and characterization of a viral α2–3-sialyltransferase (vST3Gal-I) for the synthesis of sialyl Lewisx
作者:Go Sugiarto、Kam Lau、Hai Yu、Stephanie Vuong、Vireak Thon、Yanhong Li、Shengshu Huang、Xi Chen
DOI:10.1093/glycob/cwq172
日期:2011.3
Sialyl Lewisx (SLex, Siaα2–3Galβ1–4(Fucα1–3)GlcNAcβOR) is an important sialic acid-containing carbohydrate epitope involved in many biological processes such as inflammation and cancer metastasis. In the biosynthetic process of SLex, α2–3-sialyltransferase-catalyzed sialylation generally proceeds prior to α1–3-fucosyltransferase-catalyzed fucosylation. For the chemoenzymatic synthesis of SLex containing different sialic acid forms, however, it would be more efficient if diverse sialic acid forms are transferred in the last step to the fucosylated substrate Lewisx (Lex). An α2–3-sialyltransferase obtained from myxoma virus-infected European rabbit kidney RK13 cells (viral α2–3-sialyltransferase (vST3Gal-I)) was reported to be able to tolerate fucosylated substrate Lex. Nevertheless, the substrate specificity of the enzyme was only determined using partially purified protein from extracts of cells infected with myxoma virus. Herein we demonstrate that a previously reported multifunctional bacterial enzyme Pasteurella multocida sialyltransferase 1 (PmST1) can also use Lex as an acceptor substrate, although at a much lower efficiency compared to nonfucosylated acceptor. In addition, N-terminal 30-amino-acid truncated vST3Gal-I has been successfully cloned and expressed in Escherichia coli Origami™ B(DE3) cells as a fusion protein with an N-terminal maltose binding protein (MBP) and a C-terminal His6-tag (MBP-Δ30vST3Gal-I-His6). The viral protein has been purified to homogeneity and characterized biochemically. The enzyme is active in a broad pH range varying from 5.0 to 9.0. It does not require a divalent metal for its α2–3-sialyltransferase activity. It has been used in one-pot multienzyme sialylation of Lex for the synthesis of SLex containing different sialic acid forms with good yields.
Sialyl Lewisx(SLex,Siaα2-3Galβ1-4(Fucα1-3)GlcNAcβOR)是一种重要的含硅烷基酸的碳水化合物表位,参与了许多生物过程,如炎症和癌症转移。在 SLex 的生物合成过程中,α2-3-硅氨酰基转移酶催化的硅氨酰化通常先于α1-3-岩藻糖基转移酶催化的岩藻糖基化。然而,对于含有不同硅烷基酸形式的 SLex 的化学酶法合成,如果在最后一步将不同的硅烷基酸形式转移到岩藻糖基化底物 Lewisx(Lex)上,效率会更高。据报道,从受肌瘤病毒感染的欧洲兔肾 RK13 细胞中获得的α2-3-氨酰基转移酶(病毒α2-3-氨酰基转移酶(vST3Gal-I))能够耐受岩藻糖基化底物 Lex。然而,该酶的底物特异性只能通过从感染了肌瘤病毒的细胞提取物中部分纯化的蛋白质来确定。在这里,我们证明了以前报道过的一种多功能细菌酶多杀性巴氏杆菌硅氨基转移酶 1(PmST1)也能使用 Lex 作为接受底物,不过与非岩藻糖基化接受底物相比,其效率要低得多。此外,N-末端 30 氨基酸截短的 vST3Gal-I 已被成功克隆,并在大肠杆菌 Origami™ B(DE3) 细胞中表达为与 N-末端麦芽糖结合蛋白(MBP)和 C-末端 His6 标记(MBP-Δ30vST3Gal-I-His6)的融合蛋白。病毒蛋白已被纯化至均一,并进行了生化鉴定。该酶在 5.0 到 9.0 的广泛 pH 值范围内都具有活性。它的α2-3-糖基转移酶活性不需要二价金属。它已被用于对 Lex 进行单锅多酶硅氨酰化,以合成含有不同硅氨酰形式的 SLex,而且产量很高。