Uhliariková Iveta, Vršanská Mária, McCleary Barry V, Biely Peter
Institute of Chemistry, Slovak Academy of Sciences, Bratislava, Slovakia.
Biochim Biophys Acta. 2013 Jun;1830(6):3365-72. doi: 10.1016/j.bbagen.2013.01.011. Epub 2013 Jan 30.
Microbial degradation of acetylated plant hemicelluloses involves besides enzymes cleaving the glycosidic linkages also deacetylating enzymes. A detailed knowledge of the mode of action of these enzymes is important in view of the development of efficient bioconversion of plant materials that did not undergo alkaline pretreatment leading to hydrolysis of ester linkages.
In this work deacetylation of hardwood acetylglucuronoxylan by acetylxylan esterases from Streptomyces lividans (carbohydrate esterase family 4) and Orpinomyces sp. (carbohydrate esterase family 6) was monitored by (1)H-NMR spectroscopy.
The (1)H-NMR resonances of all acetyl groups in the polysaccharide were fully assigned. The targets of both enzymes are 2- and 3-monoacetylated xylopyranosyl residues and, in the case of the Orpinomyces sp. enzyme, also the 2,3-di-O-acetylated xylopyranosyl residues. Both enzymes do not recognize as a substrate the 3-O-acetyl group on xylopyranosyl residues α-1,2-substituted with 4-O-methyl-d-glucuronic acid.
The (1)H-NMR spectroscopy approach to study positional and substrate specificity of AcXEs outlined in this work appears to be a simple way to characterize catalytic properties of enzymes belonging to various CE families.
The results contribute to development of efficient and environmentally friendly procedures for enzymatic degradation of plant biomass.
微生物对乙酰化植物半纤维素的降解除了涉及切割糖苷键的酶外，还涉及脱乙酰酶。鉴于开发未经过碱性预处理导致酯键水解的植物材料的高效生物转化方法，详细了解这些酶的作用模式非常重要。
在这项工作中，通过（1）H-NMR光谱监测了来自淡紫链霉菌（碳水化合物酯酶家族4）和奥皮诺霉菌属（碳水化合物酯酶家族6）的乙酰木聚糖酯酶对阔叶木乙酰葡糖醛酸木聚糖的脱乙酰作用。
多糖中所有乙酰基的（1）H-NMR共振均已完全归属。两种酶的作用靶点都是2-和3-单乙酰化的吡喃木糖基残基，对于奥皮诺霉菌属的酶来说，还包括2,3-二-O-乙酰化的吡喃木糖基残基。两种酶都不将被4-O-甲基-D-葡糖醛酸α-1,2-取代的吡喃木糖基残基上的3-O-乙酰基识别为底物。
本文概述的用于研究乙酰木聚糖酯酶位置和底物特异性的（1）H-NMR光谱方法似乎是表征属于各种CE家族的酶催化特性的一种简单方法。
这些结果有助于开发高效且环境友好的植物生物质酶促降解方法。
