A cold-adapted endo-fucoidanase Psf1 from Pseudoalteromonas sp. that catalyzes production of T-cell activating fucoidan oligosaccharides from Saccharina latissima fucoidan.

Bioactive sulfated fucoidans have high fucose content and are derived from brown seaweeds. Here we report the discovery of the first cold-adapted endo-α(1 → 3)-fucoidanase (EC 3.2.1.211), Psf1. The psf1 gene was found in the genome of Pseudoalteromonas sp. S3178, a bacterium isolated from a shrimp near Antarctica. Phylogenetic analyses designated Psf1 as a putative member of glycoside hydrolase family 107 (GH107). Substrate selectivity analysis confirmed Psf1 as being endo-acting and indicated that the enzyme catalyzes hydrolysis of α(1 → 3)-glycosidic fucoidan linkages. Psf1 had temperature optimum of 10-30 °C but retained activity at 1 °C. Structural modeling indicated similarity to the crystal structure of P5A_FcnA (Psychromonas sp. SW5A), yet distinct high variability regions were identified by RMSF. Psf1 released low molecular weight fucoidan oligosaccharides from Saccharina latissima fucoidan that dose-dependently reduced IL-12p40 secretion in dendritic cells, and lowered IFN-γ and IL-10 levels in dendritic cells co-cultured with allogeneic CD4 T-cells, without affecting IL-17 secretion, indicating a suppression of Th1-mediated immune response. Treatment of dendritic cells with native fucoidan from S. latissima did not affect cell viability or cytokine secretion. These findings have potential to enable new enzyme-assisted production, at low temperatures, of bioactive fucoidan oligosaccharides from S. latissima grown in the Northern Hemisphere.