Di-N-acetylchitobiase (Ctbs) degrades β-1,4 glycoside bonds of the chitobiose core of free asparagine-linked glycan. This study examined whether Ctbs degrades chitin-oligosaccharides to GlcNAc in mammals. We analyzed Ctbs mRNA and protein expression in mouse tissues and characterized enzymatic activity using recombinant mouse Ctbs expressed in Escherichia coli. Ctbs mRNA and protein were expressed in various tissues of mouse, including the stomach. Optimal conditions for recombinant Ctbs were pH 3.0 and 45°C, and the recombinant enzyme was retained more than 94% activity after incubation at pH 3.0–7.0 and below 37°C. The recombinant Ctbs hydrolyzed (GlcNAc)₃ and (GlcNAc)₆ at pH 3.0 and produced GlcNAc. The K _m of Ctbs was lowest with (GlcNAc)₃ as a substrate. k _cat/K _m was fourfold as high with (GlcNAc)₃ and (GlcNAc)₄ as substrates than with (GlcNAc)₂. These results suggest that Ctbs digests chitin-oligosaccharides or (GlcNAc)₂ of reducing-end residues of oligosaccharides and produces GlcNAc in mouse tissues.

二-N-乙酰基壳聚糖酶（Ctbs）降解游离天冬酰胺连接的聚糖的壳二糖核心的β-1,4糖苷键。这项研究检查了Ctbs是否将哺乳动物的几丁质寡糖降解为GlcNAc。我们分析了Ctbs mRNA和蛋白在小鼠组织中的表达，并利用大肠杆菌中表达的重组小鼠Ctbs表征了酶活性。Ctbs mRNA和蛋白在小鼠的各种组织（包括胃）中表达。重组Ctbs的最佳条件是pH 3.0和45°C，在pH 3.0-7.0和37°C以下孵育后，重组酶保留了超过94％的活性。重组Ctbs在pH 3.0下水解（GlcNAc）₃和（GlcNAc）₆并产生GlcNAc。该ķ 以（GlcNAc）₃为底物的Ctbs _m最低。ķ _猫/ ķ _米被四倍高与糖胺（GlcNAc）₃和葡糖胺（GlcNAc）₄作为比葡糖胺（GlcNAc）的基板₂。这些结果表明Ctbs消化几丁质寡糖或寡糖的还原末端残基（GlcNAc）₂并在小鼠组织中产生GlcNAc。