Functional variation among LPMOs revealed by the inhibitory effects of cyanide and buffer ions

• Published in: FEBS letters Vol. 599; no. 9; pp. 1317 - 1336
• Main Authors: Golten, Ole, Schwaiger, Lorenz, Forsberg, Zarah, Hall, Kelsi R., Stepnov, Anton A., Emrich‐Mills, Tom Z., Ayuso‐Fernández, Iván, Sørlie, Morten, Ludwig, Roland, Røhr, Åsmund Kjendseth, Eijsink, Vincent G. H.
• Format: Journal Article
• Language: English
• Published: England John Wiley and Sons Inc 01.05.2025
• Subjects: Bacterial Proteins - antagonists & inhibitors; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; Buffers; catalytic activity; cellulose; chitin; copper; Copper - chemistry; Copper - metabolism; cyanide; cyanides; Cyanides - chemistry; Cyanides - pharmacology; Enzyme Inhibitors - pharmacology; Enzyme Kinetics; Enzymes; Fungal Proteins - antagonists & inhibitors; Fungal Proteins - chemistry; Fungal Proteins - metabolism; fungi; Hydrogen Peroxide - chemistry; Hydrogen Peroxide - metabolism; Ions; LPMO; lytic polysaccharide monooxygenase; Mixed Function Oxygenases - antagonists & inhibitors; Mixed Function Oxygenases - chemistry; Mixed Function Oxygenases - metabolism; Oxidation-Reduction; phosphates; Phosphates - chemistry; Phosphates - pharmacology; polysaccharides; Polysaccharides - metabolism; reducing agents; copper; cyanide; lytic polysaccharide monooxygenase; LPMO; cellulose; chitin
• ISSN: 0014-5793; 1873-3468; 1873-3468
• DOI: 10.1002/1873-3468.15105

Enzymes known as lytic polysaccharide monooxygenases (LPMOs) are mono‐copper polysaccharide‐degrading peroxygenases that engage in several on‐ and off‐pathway redox reactions involving O2 and H2O2. Herein, we show that the known metalloenzyme inhibitor cyanide inhibits reductive activation of LPMOs by binding to the LPMO‐Cu(II) state and that the degree of inhibition depends on the concentrations of the polysaccharide substrate, the reductant and H2O2. Importantly, this analysis revealed differences between fungal NcAA9C and bacterial SmAA10A, which have different secondary copper coordination spheres. These differences were also highlighted by the observation that phosphate, a commonly used buffer ion, strongly inhibits NcAA9C while not affecting reactions with SmAA10A. The results provide insight into LPMO inhibition and catalysis and highlight pitfalls in the analysis thereof. This study addresses the inhibition of lytic polysaccharide monooxygenases (LPMOs) by cyanide and explains how and why the magnitude of observed inhibitory effects depends on the way LPMO reactions are setup and on the type of LPMO.