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

In 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.

The 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.

The 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.