A gene cluster involved in N-glycan metabolism was identified in the genome of Bacteroides thetaiotaomicron VPI-5482. This gene cluster encodes a major facilitator superfamily transporter, a starch utilization system-like transporter consisting of a TonB-dependent oligosaccharide transporter and an outer membrane lipoprotein, four glycoside hydrolases (alpha-mannosidase, beta-N-acetylhexosaminidase, exo-alpha-sialidase, and endo-beta-N-acetylglucosaminidase), and a phosphorylase (BT1033) with unknown function. It was demonstrated that BT1033 catalyzed the reversible phosphorolysis of beta-1,4-D-mannosyl-N-acetyl-D-glucosamine in a typical sequential Bi Bi mechanism. These results indicate that BT1033 plays a crucial role as a key enzyme in the N-glycan catabolism where beta-1,4-D-mannosyl-N-acetyl-D-glucosamine is liberated from N-glycans by sequential glycoside hydrolase-catalyzed reactions, transported into the cell, and intracellularly converted into alpha-D-mannose 1-phosphate and N-acetyl-D-glucosamine. In addition, intestinal anaerobic bacteria such as Bacteroides fragilis, Bacteroides helcogenes, Bacteroides salanitronis, Bacteroides vulgatus, Prevotella denticola, Prevotella dentalis, Prevotella melaninogenica, Parabacteroides distasonis, and Alistipes finegoldii were also suggested to possess the similar metabolic pathway for N-glycans. A notable feature of the new metabolic pathway for N-glycans is the more efficient use of ATP-stored energy, in comparison with the conventional pathway where beta-mannosidase and ATP-dependent hexokinase participate, because it is possible to directly phosphorylate the D-mannose residue of beta-1,4-D-mannosyl-N-acetyl-D-glucosamine to enter glycolysis. This is the first report of a metabolic pathway for N-glycans that includes a phosphorylase. We propose 4-O-beta-D-mannopyranosyl-N-acetyl-D-glucosamine:phosphate alpha-D-mannosyltransferase as the systematic name and beta-1,4-D-mannosyl-N-acetyl-D-glucosamine phosphorylase as the short name for BT1033.

中文翻译：

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发现参与 N-聚糖代谢的 β-1,4-D-甘露糖基-N-乙酰-D-葡糖胺磷酸化酶。

在 Bacteroides thetaiotaomicron VPI-5482 的基因组中发现了一个参与 N-聚糖代谢的基因簇。该基因簇编码一个主要的促进剂超家族转运蛋白，一种淀粉利用系统样转运蛋白，由 TonB 依赖性寡糖转运蛋白和外膜脂蛋白组成，四种糖苷水解酶（α-甘露糖苷酶、β-N-乙酰氨基己糖苷酶、外切α-唾液酸酶）和内切-β-N-乙酰氨基葡萄糖苷酶）和一种功能未知的磷酸化酶（BT1033）。结果表明，BT1033 在典型的顺序 Bi Bi 机制中催化了 β-1,4-D-甘露糖基-N-乙酰基-D-葡糖胺的可逆磷酸解。这些结果表明 BT1033 作为 N-聚糖分解代谢中的关键酶起着至关重要的作用，其中 beta-1、4-D-甘露糖基-N-乙酰-D-葡糖胺通过连续的糖苷水解酶催化反应从N-聚糖中释放出来，转运到细胞中，并在细胞内转化为α-D-甘露糖1-磷酸和N-乙酰-D -氨基葡萄糖。此外，肠道厌氧菌如脆弱拟杆菌、拟杆菌属、盐生拟杆菌、普通拟杆菌、牙普氏菌、牙普氏菌、黑色素普氏菌、副拟杆菌和细金丝菌也被认为具有相似的代谢途径。与 β-甘露糖苷酶和 ATP 依赖性己糖激酶参与的传统途径相比，N-聚糖的新代谢途径的一个显着特征是更有效地利用 ATP 储存的能量，因为可以直接磷酸化β-1,4-D-甘露糖基-N-乙酰-D-葡糖胺的D-甘露糖残基进入糖酵解。这是包含磷酸化酶的 N-聚糖代谢途径的首次报告。我们建议将 4-O-β-D-mannopyranosyl-N-acetyl-D-glucosamine:phosphate alpha-D-mannosyltransferase 作为系统名称，将 beta-1,4-D-mannosyl-N-acetyl-D-glucosamine 磷酸化酶作为系统名称BT1033 的简称。