posted on 2024-02-19, 14:03authored byXiaoqian Gu, Liping Fu, Zhiyan Wang, Zhe Cao, Luying Zhao, Dewi Seswita-Zilda, Ao Zhang, Qian Zhang, Jiang Li
Alginate
lyase Aly448, a potential new member of the polysaccharide
lyase (PL) 7 family, which was cloned and identified from the macroalgae-associated
bacterial metagenomic library, showed bifunctionality. The molecular
docking results revealed that Aly448 has two completely different
binding sites for alginate (polyMG), poly-α-l-guluronic
acid (polyG), and poly-β-d-mannuronic acid (polyM)
substrates, respectively, which might be the molecular basis for the
enzyme’s bifunctionality. Truncational results confirmed that
predicted key residues affected the bifunctionality of Aly448, but
did not wholly explain. Besides, Aly448 presented excellent biochemical
characteristics, such as higher thermal stability and pH tolerance.
Degradation of polyMG, polyM, and polyG substrates by Aly448 produced
tetrasaccharide (DP4), disaccharide (DP2), and galactose (DP1), which
exhibited excellent antioxidant activity. These findings provide novel
insights into the substrate recognition mechanism of bifunctional
alginate lyases and pave a new path for the exploitation of natural
antioxidant agents.