科研之友
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摘要
beta 1-3-N-Acetylglucosaminyltransferases (beta 3GlcNAcTs) and beta 1-4-galactosyltransferases (beta 4GalTs) have been broadly used in enzymatic synthesis of N-acetyllactosamine (LacNAc)-containing oligosaccharides and glycoconjugates including poly-LacNAc, and lacto-N-neotetraose (LNnT) found in the milk of human and other mammals. In order to explore oligosaccharides and derivatives that can be synthesized by the combination of beta 3GlcNAcTs and beta 4GalTs, donor substrate specificity studies of two bacterial beta 3GlcNAcTs from Helicobacter pylori (Hp beta 3GlcNAcT) and Neisseria meningitidis (NmLgtA), respectively, using a library of 39 sugar nucleotides were carried out. The two beta 3GlcNAcTs have complementary donor substrate promiscuity and 13 different trisaccharides were produced. They were used to investigate the acceptor substrate specificities of three beta 4GalTs from Neisseria meningitidis (NmLgtB), Helicobacter pylori (Hp beta 4GalT), and bovine (B beta 4GalT), respectively. Ten of the 13 trisaccharides were shown to be tolerable acceptors for at least one of these beta 4GalTs. The application of NmLgtA in one-pot multienzyme (OPME) synthesis of two trisaccharides including GalNAc beta 1-3Gal beta 1-4Glc beta ProN(3) and Gal beta 1-3Gal beta 1-4Glc was demonstrated. The study provides important information for using these glycosyltransferases as powerful catalysts in enzymatic and chemoenzymatic syntheses of oligosaccharides and derivatives which can be useful probes and reagents.
