9G98

Joint neutron and x-ray structure of alginate lyase PsAlg7C soaked with pentamannuronic acid

Replaces:  8RBN

Summary for 9G98

• Entry DOI: 10.2210/pdb9g98/pdb
• Related: 9G99
• Descriptor: Alginate lyase, 4-deoxy-alpha-L-erythro-hex-4-enopyranuronic acid-(1-4)-beta-D-mannopyranuronic acid, beta-D-mannopyranuronic acid-(1-4)-alpha-D-mannopyranuronic acid-(1-4)-beta-D-mannopyranuronic acid, ... (4 entities in total)
• Functional Keywords: alginate lyase, complex, beta jellyroll, alginate, lyase
• Biological source: Paradendryphiella salina
• Total number of polymer chains: 1
• Total formula weight: 26037.47

Authors

Wilkens, C.,Meilleur, F.,Morth, J.P. (deposition date: 2024-07-24, release date: 2025-07-30)

Primary citation

Rivas-Fernandez, J.P.,Vuillemin, M.,Pilgaard, B.,Klau, L.J.,Fredslund, F.,Lund-Hanssen, C.,Welner, D.H.,Meyer, A.S.,Morth, J.P.,Meilleur, F.,Aachmann, F.L.,Rovira, C.,Wilkens, C.
Unraveling the molecular mechanism of polysaccharide lyases for efficient alginate degradation.
Nat Commun, 16:2670-2670, 2025

PubMed Abstract: Alginate lyases (ALs) catalyze the depolymerization of brown macroalgae alginates, widely used naturally occurring polysaccharides. Their molecular reaction mechanism remains elusive due to the lack of catalytically competent Michaelis-Menten-like complex structures. Here, we provide structural snapshots and dissect the mechanism of mannuronan-specific ALs from family 7 polysaccharide lyases (PL7), employing time-resolved NMR, X-ray, neutron crystallography, and QM/MM simulations. We reveal the protonation state of critical active site residues, enabling atomic-level analysis of the reaction coordinate. Our approach reveals an endolytic and asynchronous syn β-elimination reaction, with Tyr serving as both Brønsted base and acid, involving a carbanion-type transition state. This study not only reconciles previous structural and kinetic discrepancies, but also establishes a comprehensive PL reaction mechanism which is most likely applicable across all enzymes of the PL7 family as well as other PL families.

PubMed: 40102416
DOI: 10.1038/s41467-025-56754-5

Experimental method

NEUTRON DIFFRACTION (2.15 Å)
X-RAY DIFFRACTION (2.1 Å)