Laboratory of Biochemistry and Protein Biotechnology, School of Arts, Sciences and Humanities, University of São Paulo, Av. Arlindo Bettio, 1000, São Paulo, CEP: 03828000, Brazil.
Laboratory of Biochemistry and Protein Biotechnology, School of Arts, Sciences and Humanities, University of São Paulo, Av. Arlindo Bettio, 1000, São Paulo, CEP: 03828000, Brazil.
Carbohydr Res. 2023 Oct;532:108901. doi: 10.1016/j.carres.2023.108901. Epub 2023 Jul 20.
Hemicelluloses are the second most abundant polysaccharide in plant biomass, in which xylan is the main constituent. Aiming at the total degradation of xylan and the obtention of fermentable sugars, several enzymes acting synergistically are required, especially β-xylosidases. In this study, β-xylosidase from Geobacillus thermodenitrificans (GtXyl) was expressed in E. coli BL21 and characterized. The enzyme GtXyl has been grouped within the family of glycoside hydrolases 43 (GH43). Results showed that GtXyl obtained the highest activity at pH 5.0 and temperature of 60 °C. In the additive's tests, the enzyme remained stable in the presence of metal ions and EDTA, and showed high tolerance to xylose, with a relative activity of 55.4% at 400 mM. The enzyme also presented bifunctional activity of β-xylosidase and α-l-arabinofuranosidase, with the highest activity on the substrate p-nitrophenyl-β-d-xylopyranoside. The specific activity on p-nitrophenyl-β-d-xylopyranoside was 18.33 U mg and catalytic efficiency of 20.21 mM s, which is comparable to other β-xylosidases reported in the literature. Putting together, the GtXyl enzyme presented interesting biochemical characteristics that are desirable for the application in the enzymatic hydrolysis of plant biomass, such as activity at higher temperatures, high thermostability and stability to metal ions.
半纤维素是植物生物质中第二丰富的多糖，其中木聚糖是主要成分。为了实现木聚糖的完全降解和获得可发酵糖，需要几种协同作用的酶，特别是β-木糖苷酶。在这项研究中，来自 Thermodenitrificans 的β-木糖苷酶（GtXyl）在大肠杆菌 BL21 中表达并进行了表征。该酶 GtXyl 属于糖苷水解酶家族 43（GH43）。结果表明，GtXyl 在 pH5.0 和 60°C 时获得最高活性。在添加剂测试中，该酶在金属离子和 EDTA 的存在下保持稳定，并且对木糖具有高耐受性，在 400mM 时相对活性为 55.4%。该酶还具有β-木糖苷酶和α-L-阿拉伯呋喃糖苷酶的双功能活性，在 p-硝基苯基-β-D-木吡喃糖苷底物上具有最高活性。对 p-硝基苯基-β-D-木吡喃糖苷的比活性为 18.33Umg，催化效率为 20.21mM s，与文献中报道的其他β-木糖苷酶相当。综上所述，GtXyl 酶具有有趣的生化特性，适用于植物生物质的酶解应用，例如在较高温度下具有活性、高热稳定性和对金属离子的稳定性。
