N-乙酰葡糖胺基转移酶-V对受体β-D-葡萄糖胺-(1→2)-α-D-甘露糖-(1→6)-β-D-葡萄糖-OR的识别：葡萄糖残基上的羟基均不重要。

Recognition of the acceptor beta-D-GlcpNAc-(1-->2)-alpha-D-Manp- (1-->6)-beta-D-Glcp-OR by N-acetyl-glucosaminyltransferase-V: none of the hydroxyl groups on the Glc-residue are important.

作者信息

Linker T, Crawley S C, Hindsgaul O

机构信息

Department of Chemistry, University of Alberta, Edmonton, Canada.

出版信息

Carbohydr Res. 1993 Jul 19;245(2):323-31. doi: 10.1016/0008-6215(93)80081-o.

DOI:10.1016/0008-6215(93)80081-o

PMID:8370029

Abstract

The enzyme, N-acetylglucosaminyltransferase-V (GlcNAcT-V, E.C. 2.4.1.155), transfer a beta-D-GlcpNAc residue, from UDP-GlcNAc, to the OH-6 group of the Man residue in the synthetic acceptor beta-D-GlcpNAc-(1-->2)-alpha-D-Manp-(1-->6)-beta-D-Glcp-O(CH2)7 CH3 (3). Trisaccharide 3 is an excellent substrate for the enzyme from hamster kidney with a Km value of 26 microM. In this paper we examine the contribution of the Glc residue in 3 to acceptor recognition by this enzyme. beta-D-GlcpNAc-(1-->2)-alpha-D-Manp-O(CH2)7CH3 where the Glc residue in 3 has been deleted, was synthesized and found to be a very poor substrate with a Km value elevated to almost 2 mM. Two other analogues of 3, where the Glc residue was O-trimethylated (6) or O-tribenzylated (7), respectively, possessed Km values very near to those of 3. The Glc residue in 3 is thereby shown to present an important recognition element for GlcNAcT-V, but none of the free hydroxyl groups are required. This observation should facilitate the design of more hydrophobic and membrane-permeable analogues of 3 that are expected to function as specific glycosylation inhibitors.

摘要

N-乙酰葡糖胺基转移酶-V（GlcNAcT-V，E.C. 2.4.1.155）可将UDP-GlcNAc中的一个β-D-GlcpNAc残基转移至合成受体β-D-GlcpNAc-(1→2)-α-D-Manp-(1→6)-β-D-Glcp-O(CH₂)₇CH₃（3）中Man残基的OH-6基团上。三糖3是仓鼠肾中该酶的优良底物，Km值为26 μM。在本文中，我们研究了3中Glc残基对该酶识别受体的贡献。合成了3中Glc残基缺失的β-D-GlcpNAc-(1→2)-α-D-Manp-O(CH₂)₇CH₃，发现它是一种很差的底物，Km值升高至近2 mM。3的另外两个类似物，其中Glc残基分别被O-三甲基化（6）或O-三苄基化（7），其Km值与3非常接近。由此表明，3中的Glc残基是GlcNAcT-V的重要识别元件，但并不需要游离羟基。这一观察结果应有助于设计出疏水性更强且具有膜通透性的3的类似物，有望作为特异性糖基化抑制剂发挥作用。