The substrate specificity of a glucoamylase with steroidal saponin-rhamnosidase activity from Curvularia lunata
The substrate specificity of a glucoamylase with steroidal saponin-rhamnosidase activity from Curvularia lunata
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新月弯孢中具有甾体皂苷鼠李糖苷酶活性的葡糖淀粉酶的底物特异性
DOI：
10.1016/j.tet.2007.04.076
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发表时间：
2007-07-16
期刊：
影响因子：
2.1
通讯作者：
Wang, Sheng-Qi
中科院分区：
文献类型：
--
作者：
Feng, Bing;Kang, Ping;Wang, Sheng-Qi
在前期工作中，我们研究并报道了来自Curvularia lunata 3.4381的一种酶对甾体皂苷C-3位末端鼠李糖基具有新的特异性，并获得了四种转化产物；该酶被纯化并确定为葡糖淀粉酶(EC 3.2.1.3 GA)。在这项工作中，对 21 种甾体皂苷和 6 种人参皂苷表现出甾体皂苷-鼠李糖苷酶活性的酶进行了系统研究。结果表明，甾体皂苷C-3位α-1,2连接的末端鼠李糖基残基可水解生成相应的次级甾体皂苷，分离鉴定出18个化合物，其中有3个新的次级化合物。对于在C-26位具有葡糖基残基的呋甾烷苷，首先在C-3位的末端鼠李糖基处发生水解，产生次级呋甾烷苷。 C-26位葡萄糖基的水解反应很大程度上取决于较长的反应时间，产生相应的二级螺甾皂苷（不含鼠李糖基和葡萄糖基残基）。该酶对甾体皂苷C-3位直链末端α-1,2-连接的鼠李糖基残基，或糖链1,4-连接糖基残基支链末端α-1,2-连接的鼠李糖基残基具有严格的特异性，对甾体皂苷糖链的不同苷元、不同糖基和糖基数目不具有特异性。人参皂苷和对硝基苯基-α-L-吡喃鼠李糖苷 (pNPR) 的末端鼠李糖基不能被来自 C. lunata 的酶水解。 (c) 2007 Elsevier Ltd. 保留所有权利。
In previous work, we studied and reported that an enzyme from Curvularia lunata 3.4381 had the novel specificity to hydrolyze the terminal rhamnosyl at C-3 position of steroidal saponin and obtained four transformed products; the enzyme was purified and ascertained as glucoamylase (EC 3.2.1.3 GA). In this work, the enzyme exhibiting steroidal saponin-rhamnosidase activity was systematically studied on 21 steroidal saponins and 6 ginsenosides. The results showed that the alpha-1,2-linked end-rhamnosyl residues at C-3 position of steroidal saponins could be hydrolyzed to corresponding secondary steroidal saponins, among which 18 compounds were isolated and identified, including 3 new secondary compounds. For the furostanosides having glucosyl residues at the C-26 position, hydrolysis occurred first at end- rhamnosyl at C-3 position to produce secondary furostanosides. The reaction of hydrolyzing glucosyl at C-26 position depended considerably on longer reaction times yielding the corresponding secondary spirostanosides ( without rhamnosyl and glucosyl residues). The enzyme had the strict specificity for the terminal alpha-1,2-linked rhamnosyl residues of linear chain, or the terminal alpha-1,2-linked rhamnosyl residues with branched chain of 1,4-linked glycosyl residues of sugar chain at C-3 position of steroidal saponins, it was not specific for different aglycones, different glycons, and the number of glycon of sugar chain of steroidal saponin. The end- rhamnosyl of ginsenosides and p-nitrophenyl-a-L-rhamnopyranoside (pNPR) could not be hydrolyzed by the enzyme from C. lunata. (c) 2007 Elsevier Ltd. All rights reserved.