Khalikova Elvira, Susi Petri, Korpela Timo
Joint Biotechnology Laboratory, Department of Chemistry, University of Turku, Finland.
Microbiol Mol Biol Rev. 2005 Jun;69(2):306-25. doi: 10.1128/MMBR.69.2.306-325.2005.
Dextran is a chemically and physically complex polymer, breakdown of which is carried out by a variety of endo- and exodextranases. Enzymes in many groups can be classified as dextranases according to function: such enzymes include dextranhydrolases, glucodextranases, exoisomaltohydrolases, exoisomaltotriohydrases, and branched-dextran exo-1,2-alpha-glucosidases. Cycloisomalto-oligosaccharide glucanotransferase does not formally belong to the dextranases even though its side reaction produces hydrolyzed dextrans. A new classification system for glycosylhydrolases and glycosyltransferases, which is based on amino acid sequence similarities, divides the dextranases into five families. However, this classification is still incomplete since sequence information is missing for many of the enzymes that have been biochemically characterized as dextranases. Dextran-degrading enzymes have been isolated from a wide range of microorganisms. The major characteristics of these enzymes, the methods for analyzing their activities and biological roles, analysis of primary sequence data, and three-dimensional structures of dextranases have been dealt with in this review. Dextranases are promising for future use in various scientific and biotechnological applications.
右旋糖酐是一种化学和物理性质复杂的聚合物，其降解由多种内切和外切右旋糖酐酶进行。根据功能，许多组中的酶可归类为右旋糖酐酶：这类酶包括右旋糖酐水解酶、葡糖右旋糖酐酶、外切异麦芽糖水解酶、外切异麦芽三糖水解酶和支链右旋糖酐外切1,2-α-葡糖苷酶。环异麦芽糖寡糖葡聚糖转移酶虽然其副反应会产生水解的右旋糖酐，但并不正式属于右旋糖酐酶。一种基于氨基酸序列相似性的糖基水解酶和糖基转移酶新分类系统将右旋糖酐酶分为五个家族。然而，由于许多已被生物化学表征为右旋糖酐酶的酶缺少序列信息，这种分类仍然不完整。已从多种微生物中分离出右旋糖酐降解酶。本文综述了这些酶的主要特性、分析其活性和生物学作用的方法、一级序列数据的分析以及右旋糖酐酶的三维结构。右旋糖酐酶在未来各种科学和生物技术应用中具有广阔前景。
