Preparation and anti-inflammation activity of λ-carrageenan oligosaccharides degraded by a novel λ-carrageenase Car3193.

To date, less attention has been paid to λ-carrageenases and their enzymatic hydrolysates than to κ- and ι-carrageenases and their hydrolysates. In this study, a Gram-negative strain Polaribacter sp. NJDZ03 was isolated from the surface of an Antarctic macroalga, Desmarestia sp., and a novel λ-carrageenase gene car3193 was isolated from it. The car3193 gene was 2832 bp long, and encoded an enzyme consisting of 943 amino acids. Although Car3193 had the typical PQQ structure at the N-terminal, its predicted active sites, Arg93 and Asn361, differed from those of other reported λ-carrageenases. The optimum temperature and pH of recombinant Car3193 towards λ-carrageenan were 50 °C and 7.0, respectively. The degradation products of λ-carrageenan produced by Car3193 were λ-neocarrabiose-, λ-neocarratetraose-, and λ-neocarraoctose-saccharides. Two products of enzymatic hydrolysis, λ-COs-1 (degree of polymerization 2; DP2) and λ-CO2 (DP8), showed excellent anti-inflammatory activity towards lipopolysaccharide-induced RAW264.7 macrophages. Treatment with λ-COs-1 (DP2) and λ-CO2 (DP8) significantly inhibited the secretion of the pro-inflammatory factors TNF-α, IL-6, IL-1β, and NO by RAW264.7 macrophages, and stimulated the secretion of the anti-inflammatory factors TGF-β1 and IL-10. The anti-inflammatory activity of λ-COs-1 was stronger than that of λ-CO-2, and λ-COs-1 had a dose-dependent bioactive effect, whereas λ-CO-2 did not. Further analyses showed that these carrageenan oligomers stimulated an anti-inflammatory response by inhibiting the NF-κB signaling pathway. Car3193 has potential applications in industry because of its high activity and strong stability, and its ability to generate bioactive products.