A novel transglycosylation strategy for efficient preparation of N-acetyllactosamine (Gal beta1 --> 4GlcNAc, LacNAc) and sialyl LacNAc was developed using beta -galactosidase from Bacillus circulans. In order to minimize the competing hydrolysis by forcing the enzymatic transglycosylation to proceed in an intramolecular manner, a novel substrate 9 carrying the donor (galactose) and the acceptor (N-acetylglucosamine) components linked via a 2-hydroxy-5-nitro-benzylalcohol derived tether was prepared. Treatment with beta -galactosidase from B. circulans afforded the transglycosylation product 11 in 26% yield. Furthermore, addition of sialyltransferase and CMP-sialic acid to this system gave sialyl LacNAc 18 in 39% yield. (C) 2001 Elsevier Science Ltd. All rights reserved.
Novel substrates for efficient enzymatic transglycosylation byBacillus circulans
摘要:
为了高效制备N-乙酰乳糖胺(Galβ(1[Formula: see text]4)GlcNAc,LacNAc),探索了β-半乳糖苷酶介导的转糖基化,使用新型底物枯草杆菌环状芽孢杆菌。为了使转糖基化在熵上有利于水解,供体(乳糖或半乳糖)和受体(N-乙酰葡萄糖胺,GlcNAc)组分连接到单个分子上。为此,筛选了1,2-和1,3-苯二甲醇以及2-羟基-5-硝基-和5-羟基-2-硝基苄醇作为连接剂,并在几种条件下研究了酶促转糖基化。在2-羟基-5-硝基苄连接底物40的情况下,观察到了分子内转糖基化的迹象,并以26%的分离产率获得了期望产物(58)。在CMP唾液酸和α-(2[Formula: see text]6)-唾液酰基转移酶存在的情况下,同一反应在一个锅中以39%的分离产率得到了唾液酰基LacNAc 87。此外,简要考察了受体组分的C-2取代基的影响,使用含有NHAlloc(72)、NHTroc(73)和N3(74)基团的底物。尽管在这些情况下分子内转糖基化的发生并不明确,但获得了8183的二糖以合理的产率。关键词:半乳糖苷酶,分子内转糖基化,N-乙酰乳糖胺,唾液酰基转移酶。