Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Gachibowli, Hyderabad 500 046, Telangana, India.
School of Chemistry, University of Hyderabad, Gachibowli, Hyderabad 500 046, Telangana, India.
J Agric Food Chem. 2021 Jan 13;69(1):78-87. doi: 10.1021/acs.jafc.0c05078. Epub 2021 Jan 3.
Chitooligosaccharides (COS) generated from either chitin (chitin oligosaccharides) or chitosan (chitosan oligosaccharides) have a wide range of applications in agriculture, medicine, and other fields. Here, we report the characterization of a chitosanase from (Csn) and the importance of a tryptophan (Trp), W204, for Csn activity. Csn hydrolyzed the chitosan polymer by an endo mode. It also hydrolyzed chitin oligosaccharides and interestingly exhibited transglycosylation activity on chitotetraose and chitopentaose. Mutation of W204, a nonconserved amino acid in chitosanases, to W204A abolished the hydrolytic activity of Csn, with a change in the structure that resulted in a decreased affinity for the substrate and impaired the catalytic ability. Phylogenetic analysis revealed that Csn could belong to a new class of chitosanases that showed unique properties like transglycosylation, cleavage of chitin oligosaccharides, and the presence of W204 residues, which is important for activity. Chitosanases belonging to the Csn class showed a high potential to generate COS from chitinous substrates.
壳寡糖（COS）无论是由壳聚糖（壳寡糖）或几丁聚糖（几丁寡糖）产生，都在农业、医学和其他领域有广泛的应用。在这里，我们报道了几丁聚糖酶的特征（Csn）和色氨酸（Trp），W204，对 Csn 活性的重要性。Csn 通过内切模式水解壳聚糖聚合物。它还水解壳寡糖，并且有趣的是在几丁四糖和几丁五糖上表现出转糖苷活性。色氨酸（Trp），W204，在几丁聚糖酶中是非保守氨基酸，突变到 W204A 使 Csn 的水解活性丧失，结构发生变化导致对底物的亲和力降低，催化能力受损。系统发育分析表明，Csn 可能属于一类新的几丁聚糖酶，具有独特的性质，如转糖苷、壳寡糖的切割和 W204 残基的存在，这对活性很重要。属于 Csn 类的几丁聚糖酶具有从壳质底物生成 COS 的高潜力。
