Hashimoto W, Kobayashi E, Nankai H, Sato N, Miya T, Kawai S, Murata K
Research Institute for Food Science, Kyoto University, Uji, 611-0011, Japan.
Arch Biochem Biophys. 1999 Aug 15;368(2):367-74. doi: 10.1006/abbi.1999.1305.
The bacterium Bacillus sp. GL1 assimilates two kinds of heteropolysaccharides, gellan and xanthan, by using extracellular gellan and xanthan lyases, respectively, and produces unsaturated saccharides as the first degradation products. A novel unsaturated glucuronyl hydrolase (glycuronidase), which was induced in the bacterial cells grown on either gellan or xanthan, was found to act on the tetrasaccharide of unsaturated glucuronyl-glucosyl-rhamnosyl-glucose produced from gellan by gellan lyase, and the enzyme and its gene were isolated from gellan-grown cells. The nucleotide sequence showed that the gene contained an ORF consisting of 1131 base pairs coding a polypeptide with a molecular weight of 42,859. The purified enzyme was a monomer with a molecular mass of 42 kDa and was most active at pH 6.0 and 45 degrees C. Because the enzyme can act not only on the gellan-degrading product by gellan lyase, but also on unsaturated chondroitin and hyaluronate disaccharides produced by chondroitin and hyaluronate lyases, respectively, it is considered that the unsaturated glucuronyl hydrolase plays specific and ubiquitous roles in the degradation of oligosaccharides with unsaturated uronic acid at the nonreducing terminal produced by polysaccharide lyases.
芽孢杆菌属GL1通过分别利用胞外结冷胶酶和黄原胶酶来同化两种杂多糖，即结冷胶和黄原胶，并产生不饱和糖类作为最初的降解产物。在以结冷胶或黄原胶为生长底物的细菌细胞中诱导产生了一种新型不饱和葡糖醛酸水解酶（葡糖醛酸酶），该酶作用于结冷胶酶作用结冷胶产生的不饱和葡糖醛酸基-葡糖基-鼠李糖基-葡萄糖四糖，并且从以结冷胶为生长底物的细胞中分离出了该酶及其基因。核苷酸序列显示该基因包含一个由1131个碱基对组成的开放阅读框，编码一个分子量为42859的多肽。纯化后的酶是一种分子量为42 kDa的单体，在pH 6.0和45℃时活性最高。由于该酶不仅可以作用于结冷胶酶降解结冷胶产生的产物，还可以分别作用于软骨素酶和透明质酸酶产生的不饱和软骨素二糖和透明质酸二糖，因此认为不饱和葡糖醛酸水解酶在多糖裂解酶产生的非还原端带有不饱和糖醛酸的寡糖降解中发挥着特定且普遍的作用。
