[Recent advances in structures and relative enzyme properties of xylanase].

Xylanase can hydrolyze xylans into xylooligosaccharides and D-xylose, and has great prospect for applications in feed industry, paper and pulp industry, food industry and environment science. The study of xylanase had been started in 1960's. With the development and application of the new technologies, such as molecular biology, structural biology and protein engineering, many progresses have been made in the research of structures and functions of xylanase. This paper reviews the research progress and trend in the structure correlating with the important properties of xylanase. Analyses of three-dimensional structures and properties of mutants have revealed that glutamine and aspartic acid residues are involved in the catalytic mechanism. The thermostability of xylanase correlated with many factors, such as disulfide bridges, salt bridges, aromatic interactions, cotent of arginine and proline, and some multidomain xylanase have thermostability domains in N or C terminal. But no single mechanism is responsible for the remarkable stability of xylanase. The isoelectic points and reaction pH of xylanase are influenced by hydrophobicity and content of electric charges. Many researches had demonstrated that aromatic amino acid, histidine, and tryptophan play an important role in improving enzyme-substrate affinity. The researches of structures and functions of xylanase are of great significance in understanding the catalytic mechanism and directing the improvement of xylanase properties to meet the application requirement.