引用本文:	孟雪,李爽,张杰,段德麟.海带(Saccharina japonica)甘露糖醛酸C5异构酶的功能分析[J].海洋科学,2025,49(6):15-24.

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*海带(Saccharina japonica)甘露糖醛酸C5异构酶的功能分析*
孟雪^1,2,3, 李爽^1,2,3, 张杰^1,2, 段德麟^1,2
1.中国科学院海洋研究所/实验海洋生物学重点实验室, 山东青岛 266000;2.青岛海洋科技中心海洋生物学与生物技术功能实验室, 山东青岛 266000;3.中国科学院大学, 北京 100049

摘要:

褐藻胶是由β-D-甘露糖醛酸(M)及其C5反向异构体α-L-古罗糖醛酸(G)组成的线性聚合物,是海带(Saccharina japonica)中重要的碳代谢产物,目前广泛应用于食品、医药、纺织和农业等工业领域,甘露糖醛酸C5异构酶(Mannuronan C5-epimerase,简称MC5E)是褐藻胶生物合成途径中一种重要的修饰酶,它能催化β-D-甘露糖醛酸(β-D-mannuronic acid,简称M)转化成α-L-古罗糖醛酸(α-L-guluronic acid,简称G)。本研究从海带基因组数据库中筛选并分离到了一个高表达的SjMC5E3序列,将其转化到大肠杆菌中实现体外表达并进行蛋白纯化,通过核磁共振光谱分析测量其酶活性,结果表明,SjMC5E3可以转化并提高褐藻胶中G残基的含量,降低产物中M/G比值,M/G比值为4.63。本研究揭示了MC5E在褐藻酸合成途径中的关键作用,对高G含量褐藻胶的生产以及合成具有重要意义,将对未来褐藻胶产品的工业化制备提供技术支持。

关键词: 海带甘露糖醛酸C5异构酶褐藻胶

DOI：10.11759/hykx20250225003

分类号:Q55

基金项目:外交部中国-印尼海洋牧场建设与示范项目(2020WJB06);青岛国际合作项目(22-3-6-ghgg-1-hz)

Functional analysis of mannuronan C5-epimerases from Saccharina japonica

MENG Xue^1,2,3, LI Shuang^1,2,3, ZHANG Jie^1,2, DUAN Delin^1,2

1.Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266000, China;2.Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao 266000, China;3.University of Chinese Academy of Sciences, Beijing 100049, China

Abstract:

Alginate, a linear polymer of β-D-mannuronic acid (M) and its C5 epimer α-L-guluronic acid (G), serves as a crucial carbon metabolite for the brown alga Saccharina japonica. Alginate is widely used in industries such as food, medicine, textiles, and agriculture. Mannuronan C5-epimerase (MC5E) is a critical enzyme of the alginate biosynthesis pathway that catalyzes the epimerization of M to G. This study identified a highly expressed SjMC5E3 sequence from the genome of S. japonica and isolated it. It was used to transform Escherichia coli for in vitro expression. The protein synthesized was purified. Enzyme assays utilizing Proton Nuclear Magnetic Resonance Spectroscopy demonstrated an M/G ratio of 4.63 in the SjMC5E3-catalyzed reaction products, confirming its capability to convert M residues in alginate to G residues. Thus, this study reveals the vital role of MC5E in the alginate biosynthesis pathway, which is of great relevance for the production of alginate with a high G content, and can provide technical support for the industrial-scale preparation of alginate products in the future.

Key words: Saccharina japonica mannuronan C5-epimerase alginate