Synthesis of the acceptor analog αFuc(1→2)αGal-O(CH2)7 CH3: A probe for the kinetic mechanism of recombinant human blood group B glycosyltransferase
Synthesis of the acceptor analog αFuc(1→2)αGal-O(CH2)7 CH3: A probe for the kinetic mechanism of recombinant human blood group B glycosyltransferase
复制标题
受体类似物αFuc(1→2)αGal-O(CH2)7 CH3的合成：重组人B血型糖基转移酶动力学机制的探针
作者：
V. Kamath;N. Seto;C. A. Compston;O. Hindsgaul;M. Palcic
本文报道了天然血型（O）H二糖α Fuc（1→2）β Gal-OR类似物α Fuc（1 → 2）α Gal-O（CH 2）7 CH 3（1）的化学合成。化合物1是重组血型B糖基转移酶（GTB）的良好底物，并用作酶促合成血型B类似物αGal（→3）[αFuc（1→2）]αGal-O（CH 2）7 CH 3（2）的前体。为了探索GTB反应的机理，使用化合物1或天然受体二糖αFuc（1→2）βGal-O（CH 2）7 CH 3（3）与UDP-Gal和UDP-GalNAc供体进行动力学评估。替代供体和受体对的动力学常数的比较表明，GTB机制是Theorell-Chance，其中供体结合先于受体结合。GTB在供体的异头中心保留构型的情况下操作。保留反应被认为是通过双置换机制发生的，形成了与所提出的Theorell-Chance机制一致的糖基-酶中间体。
We report the chemical synthesis of αFuc(1→2)αGal-O(CH2)7CH3 (1) an analog of the natural blood group (O)H disaccharide αFuc(1→2)βGal-OR. Compound 1 was a good substrate for recombinant blood group B glycosyltransferase (GTB) and was used as a precursor for the enzymatic synthesis of the blood group B analog αGal(→3)[αFuc(1→2)]αGal-O(CH2)7CH3 (2). To probe the mechanism of the GTB reaction, kinetic evaluations were carried out employing compound 1 or the natural acceptor disaccharide αFuc(1→2)βGal-O(CH2)7CH3 (3) with UDP-Gal and UDP-GalNAc donors. Comparisons of the kinetic constants for alternative donor and acceptor pairs suggest that the GTB mechanism is Theorell-Chance where donor binding precedes acceptor binding. GTB operates with retention of configuration at the anomeric center of the donor. Retaining reactions are thought to occur via a double-displacement mechanism with formation of a glycosyl-enzyme intermediate consistent with the proposed Theorell-Chance mechanism.