The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China; The Science Center for Future Foods, Jiangnan University, Wuxi 214122, China.
The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China.
Carbohydr Polym. 2022 Feb 1;277:118838. doi: 10.1016/j.carbpol.2021.118838. Epub 2021 Nov 2.
Hyaluronidases have attracted a great deal of interest in the field of medicine due to their fundamental roles in the breakdown of hyaluronan. However, little is known about the catalytic mechanism of the hyaluronate 3-glycanohydrolases. Here, we report the crystal structure and cleavage pattern of a leech hyaluronidase (LHyal), which hydrolyzes the β-1,3-glycosidic bonds of hyaluronan. LHyal exhibits the typical structural features of glycoside hydrolase 79 family but contains a variable 'exo-pocket' loop where basic residues R102 and K103 are the structural determinants of hyaluronan binding. Through analysis of the hydrolysis of even- and odd-numbered hyaluronan oligosaccharides, we demonstrate that hexasaccharide is the shortest natural substrate, which can be cleaved from both the reducing and non-reducing ends to release disaccharides, and pentasaccharides are the smallest fragments for recognition and hydrolysis. These observations provide new insights into the degradation of hyaluronan and the evolutionary relationships of the GH79 family enzymes.
透明质酸酶因其在透明质酸分解中的基本作用而在医学领域引起了极大的关注。然而，关于透明质酸盐 3-糖基水解酶的催化机制知之甚少。在这里，我们报告了一种水蛭透明质酸酶（LHyal）的晶体结构和裂解模式，它水解透明质酸的β-1,3-糖苷键。LHyal 表现出糖苷水解酶 79 家族的典型结构特征，但含有一个可变的“外口袋”环，其中碱性残基 R102 和 K103 是透明质酸结合的结构决定因素。通过分析偶数和奇数号透明质酸寡糖的水解，我们证明六糖是最短的天然底物，可以从还原端和非还原端切割释放二糖，而五糖是识别和水解的最小片段。这些观察结果为透明质酸的降解和 GH79 家族酶的进化关系提供了新的见解。
