海带(Saccharina japonica)甘露糖醛酸C5异构酶的功能分析OA北大核心

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 ex-pression.The protein synthesized was purified.Enzyme assays utilizing Proton Nuclear Magnetic Resonance Spec-troscopy 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 bio-synthesis 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.