Serratia marcescens chitobiase is a retaining glycosidase utilizing substrate acetamido group participation
Serratia marcescens chitobiase is a retaining glycosidase utilizing substrate acetamido group participation
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DOI：
10.1042/bj3280945
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发表时间：
1997-12-15
影响因子：
4.1
通讯作者：
Henrissat, B
中科院分区：
文献类型：
--
作者：
Drouillard, S;Armand, S;Henrissat, B
通过HPLC分离对硝基苯基N-乙酰-β-D-氨基葡萄糖苷（PNP-GlcNAc）水解过程中产生的N-乙酰氨基葡萄糖的端基异构体，确定了粘质沙雷氏菌壳二糖酶催化反应的立体化学。在反应的早期阶段，发现β-端基异构体占主导地位，而α-端基异构体占主导地位的变旋平衡。这证明壳聚糖酶水解糖苷键，并总体保留异头构型。壳聚糖酶催化PNP-GlcNAc的水解被一系列在其非还原端选择性脱N-乙酰化的壳寡糖（聚合度2-5）竞争性抑制。这与底物C-2位乙酰氨基参与壳聚糖酶及相关酶的催化机理是雅阁的。
The stereochemistry of the reaction catalysed by Serratia marcescens chitobiase was determined by HPLC separation of the anomers of N-acetylglucosamine produced during the hydrolysis of p-nitrophenyl N-acetyl-beta-D-glucosaminide (PNP-GlcNAc). In the early stages of the reaction, the beta-anomer was found to prevail, whereas the alpha-anomer dominated at mutarotation equilibrium. This established that chitobiase hydrolyses glycosidic bonds with overall retention of the anomeric configuration. Chitobiase-catalysed hydrolysis of PNP-GlcNAc was competitively inhibited by a series of chito-oligosaccharides (degree of polymerization 2-5) that were selectively de-N-acetylated at their non-reducing end. The results are in accord with the participation of the acetamido group at C-2 of the substrate in the catalytic mechanism of chitobiase and related enzymes.