Zeng X, Yoshino R, Murata T, Ajisaka K, Usui T
Department of Applied Biological Chemistry, Faculty of Agriculture, Shizuoka University, Ohya, Japan.
Carbohydr Res. 2000 Apr 7;325(2):120-31. doi: 10.1016/s0008-6215(99)00303-1.
The beta-D-galactosidase from porcine liver induced regiospecific transglycosylation of beta-D-galactose from beta-D-Gal-OC6H4NO2-o to OH-6 of, respectively, p-nitrophenyl glycoside acceptors of Gal, GlcNAc and GalNAc to afford beta-Gal-(1-->6)-alpha-Gal-OC6H4NO2-p, beta-Gal-(1--> 6)-beta-Gal-OC6H4NO2-p, beta-Gal-(1-->6)-alpha-GalNAc-OC6H4NO2-p, beta-Gal-(1-->6)-beta-GalNAc-OC6H4NO2-p, beta-Gal-(1-->6)-alpha-GlcNAc-OC6H4NO2-p, and beta-Gal-(1-->6)-beta-GlcNAc-OC6H4NO2-p. The enzyme showed much higher transglycosylation activity for the alpha-glycoside acceptors than the corresponding beta-glycoside acceptors. The regioselectivity of the beta-D-galactosidase from Bacillus circulans ATCC 31382 greatly depended on the nature of the acceptor. When alpha-D-GalNAc-OC6H4NO2-p and alpha-D-GlcNAc-OC6H4NO2-p were used as acceptors, the enzyme showed high potency for regioselective synthesis of beta-Gal-(1-->3)-alpha-GalNAc-OC6H4NO2-p and beta-Gal-(1-->3)-alpha-GlcNAc-OC6H4NO2-p in high respective yields of 75.9 and 79.3% based on the acceptors added. However, replacement of beta-D-Gal-OC6H4NO2-p by beta-D-GalNAc-OC6H4NO2-p did change the direction of galactosylation. The enzyme formed regioselectively beta-Gal-(1-->6)-beta-Gal-OC6H4NO2-p with (beta-Gal-1-->(6-beta-Gal-1-->)n6-beta-Gal-OC6H4NO2-p, n = 1-4). No beta-(1-->3)-linked product was detected during the reaction. Use of the two readily available beta-D-galactosidases facilitates the preparation of (1-->3)- and (1-->6)-linked disaccharide glycosides of beta-D-Gal-GalNAc and beta-D-Gal-GlcNAc.
猪肝中的β-D-半乳糖苷酶可诱导β-D-半乳糖从β-D-Gal-OC6H4NO2-o分别向Gal、GlcNAc和GalNAc的对硝基苯基糖苷受体的OH-6进行区域特异性转糖基化反应，生成β-Gal-(1→6)-α-Gal-OC6H4NO2-p、β-Gal-(1→6)-β-Gal-OC6H4NO2-p、β-Gal-(1→6)-α-GalNAc-OC6H4NO2-p、β-Gal-(1→6)-β-GalNAc-OC6H4NO2-p、β-Gal-(1→6)-α-GlcNAc-OC6H4NO2-p和β-Gal-(1→6)-β-GlcNAc-OC6H4NO2-p。该酶对α-糖苷受体的转糖基化活性比对相应β-糖苷受体的活性高得多。环状芽孢杆菌ATCC 31382来源的β-D-半乳糖苷酶的区域选择性很大程度上取决于受体的性质。当使用α-D-GalNAc-OC6H4NO2-p和α-D-GlcNAc-OC6H4NO2-p作为受体时，该酶在基于添加受体的75.9%和79.3%的高各自产率下，对β-Gal-(1→3)-α-GalNAc-OC6H4NO2-p和β-Gal-(1→3)-α-GlcNAc-OC6H4NO2-p的区域选择性合成表现出高效能。然而，用β-D-GalNAc-OC6H4NO2-p替代β-D-Gal-OC6H4NO2-p确实改变了半乳糖基化的方向。该酶区域选择性地形成了β-Gal-(1→6)-β-Gal-OC6H4NO2-p与(β-Gal-1→(6-β-Gal-1→)n6-β-Gal-OC6H4NO2-p，n = 1 - 4)。反应过程中未检测到β-(1→3)连接的产物。使用这两种易于获得的β-D-半乳糖苷酶有助于制备β-D-Gal-GalNAc和β-D-Gal-GlcNAc的(→3)-和(→6)-连接的二糖糖苷。
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