Identification and characterization of ι‐carrageenase from macroalgae‐associated bacterium Microbulbifer sp. YNDZ01

Abstract

AbstractBACKGROUNDIn the present study, the ι‐carrageenase gene, Car1293, was obtained from the genome of Microbulbifer sp. YNDZ01, which was isolated from the surface of macroalgae. To date, there are few studies on ι‐carrageenase and the anti‐inflammatory activity of ι‐carrageenan oligosaccharides (CGOS). To enhance our perspective on ι‐carrageenase and ι‐carrageen oligosaccharides, the sequence, protein structure, enzymatic properties, enzymatic digestion products and anti‐inflammatory activity of the gene were investigated.RESULTSThe gene length of Car1293 is 2,589 bp, encoding an enzyme with 862 amino acids, which shares 34% similarity with any previously reported ι‐carrageenase. The spatial structure of Car1293 consists of many α‐helices with a β‐fold binding module located at its terminus, and eight binding sites were found in the binding module as a result of docking with CGOS‐DP4 ligand. The optimum temperature and pH for the activity of recombinant Car1293 toward ι‐carrageenan were 50 °C and 6.0, respectively. The hydrolysates of Car1293 are mainly degree of polymerization (DP)8, with minor products showing DP2, DP4, and DP6. The enzymatic hydrolysates CGOS‐DP8 showed prominent anti‐inflammatory activity, which was greater than that of the positive control l‐monomethylarginine in lipopolysaccharide‐induced RAW264.7 macrophages. It inhibited nitric oxide production, as well as significantly inhibited tumor necrosis factor‐α and interleukin‐6 secretion.CONCLUSIONThe ι‐carrageenase sequence encoded by Car1293 is novel and can hydrolyze carrageenan into CGOS‐DP8 that has a significant anti‐inflammatory effect. The present study fills a gap in the research on the biological activity of oligosaccharides in ι‐carrageenan and provides promising data for the development of natural anti‐inflammatory agent. © 2023 Society of Chemical Industry.