Fuente: PubMed "microbial biotechnology" Int J Biol Macromol. 2025 Nov 28:149298. doi: 10.1016/j.ijbiomac.2025.149298. Online ahead of print.ABSTRACTAs one of the primary structural components in green algal cell walls, ulvan can be enzymatically degraded by ulvan lyase to produce oligosaccharides with diverse biological activities. In this study, TsUly40A, a new PL40 family ulvan lyase from Thalassomonas sp. LD5, was characterized as an endo-acting enzyme that degrades ulvan into ΔRha3S-disaccharide via β-elimination. The enzyme exhibited optimal activity at 45 °C and pH 7.3, with remarkable stability across a broad pH range (6.0-10.0) and NaCl tolerance (0-1.5 M). AlphaFold3 predicts an architecture comprising an N-terminal (α/α)6-helical barrel and a C-terminal β-sheet domain, forming an electropositive catalytic pocket at the interface. Molecular docking and comparative analysis with structurally similar polysaccharide lyases identified conserved residues, Asn211, Tyr271, and His446, as critical catalytic sites. Site-directed mutagenesis confirmed their essential roles, while mutants N211A, Y271A, and H446A completely lost enzymatic activity. This study provided the first structural and mechanistic insights into the PL40 family, advancing understanding of ulvan lyase diversity and catalytic strategies.PMID:41319761 | DOI:10.1016/j.ijbiomac.2025.149298