School of Biomolecular Science and Engineering (BSE), Vidyasirimedhi Institute of Science and Technology (VISTEC), Payunai, Wangchan District, Rayong 21210, Thailand.
Department of Advanced Bioscience, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Japan.
Molecules. 2023 Sep 13;28(18):6591. doi: 10.3390/molecules28186591.
Chitooligosaccharides (COSs) are b-1,4-linked homo-oligosaccharides of -acetylglucosamine (GlcNAc) or glucosamine (GlcN), and also include hetero-oligosaccharides composed of GlcNAc and GlcN. These sugars are of practical importance because of their various biological activities, such as antimicrobial, anti-inflammatory, antioxidant and antitumor activities, as well as triggering the innate immunity in plants. The reported data on bioactivities of COSs used to contain some uncertainties or contradictions, because the experiments were conducted with poorly characterized COS mixtures. Recently, COSs have been satisfactorily characterized with respect to their structures, especially the degree of polymerization (DP) and degree of -acetylation (DA); thus, the structure-bioactivity relationship of COSs has become more unambiguous. To date, various green-chemical strategies involving enzymatic synthesis of COSs with designed sequences and desired biological activities have been developed. The enzymatic strategies could involve transglycosylation or glycosynthase reactions using reducing end-activated sugars as the donor substrates and chitinase/chitosanase and their mutants as the biocatalysts. Site-specific chitin deacetylases were also proposed to be applicable for this purpose. Furthermore, to improve the yields of the COS products, metabolic engineering techniques could be applied. The above-mentioned approaches will provide the opportunity to produce tailor-made COSs, leading to the enhanced utilization of chitin biomass.
壳寡糖（COSs）是由β-1,4-连接的乙酰氨基葡萄糖（GlcNAc）或氨基葡萄糖（GlcN）组成的同型寡糖，也包括由 GlcNAc 和 GlcN 组成的杂合寡糖。由于其具有各种生物活性，如抗菌、抗炎、抗氧化和抗肿瘤活性，以及在植物中触发先天免疫，这些糖具有实际重要性。用于生物活性的 COS 报道数据包含一些不确定性或矛盾，因为这些实验是使用特征不明确的 COS 混合物进行的。最近，COS 的结构，特别是聚合度（DP）和乙酰化度（DA）得到了令人满意的描述，因此，COS 的结构-生物活性关系变得更加明确。迄今为止，已经开发了各种涉及酶法合成具有设计序列和所需生物活性的 COS 的绿色化学策略。酶法策略可以涉及使用还原端活化糖作为供体底物的转糖苷或糖基合成酶反应，以及壳聚糖酶/壳聚糖酶及其突变体作为生物催化剂。还提出了特异性壳质去乙酰化酶可用于此目的。此外，为了提高 COS 产物的产率，可以应用代谢工程技术。上述方法将为定制 COS 的生产提供机会，从而提高甲壳素生物质的利用率。
