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

Abstract

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