Spániková Silvia, Poláková Monika, Joniak Dusan, Hirsch Ján, Biely Peter
Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 38, Bratislava, Slovakia.
Arch Microbiol. 2007 Aug;188(2):185-9. doi: 10.1007/s00203-007-0241-x. Epub 2007 Apr 18.
Glucuronoyl esterase is a novel carbohydrate esterase recently discovered in the cellulolytic system of the wood-rotting fungus Schizophyllum commune on the basis of its ability to hydrolyze methyl ester of 4-O-methyl-D-glucuronic acid. This substrate was not fully corresponding to the anticipated function of the enzyme to hydrolyze esters between xylan-bound 4-O-methyl-D-glucuronic acid and lignin alcohols occurring in plant cell walls. In this work we showed that the enzyme was capable of hydrolyzing two synthetic compounds that mimic the ester linkages described in lignin-carbohydrate complexes, esters of 4-O-methyl-D-glucuronic and D-glucuronic acid with 3-(4-methoxyphenyl)propyl alcohol. A comparison of kinetics of hydrolysis of methyl and 3-(4-methoxyphenyl)propyl esters indicated that the glucuronoyl esterase recognizes the uronic acid part of the substrates better than the alcohol type. The catalytic efficiency of the enzyme was much higher with the ester of 4-O-methyl-D-glucuronic acid than with that of D-glucuronic acid. Examination of the action of glucuronoyl esterase on a series of methyl esters of 4-O-methyl-D-glucopyranuronosyl residues alpha-1,2-linked to xylose and several xylooligosaccharides suggested that the rate of deesterification is independent of the character of the carbohydrate part glycosylated by the 4-O-methyl-D-glucuronic acid.
葡糖醛酸酯酶是一种新型碳水化合物酯酶，最近在木腐真菌裂褶菌的纤维素分解系统中被发现，基于其能够水解4-O-甲基-D-葡糖醛酸甲酯的能力。这种底物并不完全符合该酶水解植物细胞壁中木聚糖结合的4-O-甲基-D-葡糖醛酸与木质素醇之间酯键的预期功能。在这项工作中，我们表明该酶能够水解两种模拟木质素-碳水化合物复合物中所述酯键的合成化合物，即4-O-甲基-D-葡糖醛酸和D-葡糖醛酸与3-(4-甲氧基苯基)丙醇形成的酯。甲基酯和3-(4-甲氧基苯基)丙酯水解动力学的比较表明，葡糖醛酸酯酶识别底物的糖醛酸部分比醇部分更好。该酶对4-O-甲基-D-葡糖醛酸酯的催化效率远高于对D-葡糖醛酸酯的催化效率。对葡糖醛酸酯酶作用于一系列α-1,2-连接到木糖的4-O-甲基-D-吡喃葡糖醛酸残基的甲酯以及几种木寡糖的研究表明，脱酯速率与被4-O-甲基-D-葡糖醛酸糖基化的碳水化合物部分的性质无关。
