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Research article - Peer-reviewed, 2016

Interactions of a fungal lytic polysaccharide monooxygenase with beta-glucan substrates and cellobiose dehydrogenase

Courtade, Gaston; Dimarogona, Maria; Sandgren, Mats; Eijsink, Vincent G. H.; Lillelund Aachmann, Finn

Abstract

Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes that catalyze oxidative cleavage of glycosidic bonds using molecular oxygen and an external electron donor. We have used NMR and isothermal titration calorimetry (ITC) to study the interactions of a broad-specificity fungal LPMO, NcLPMO9C, with various substrates and with cellobiose dehydrogenase (CDH), a known natural supplier of electrons. The NMR studies revealed interactions with cellohexaose that center around the copper site. NMR studies with xyloglucans, i. e., branched beta-glucans, showed an extended binding surface compared with cellohexaose, whereas ITC experiments showed slightly higher affinity and a different thermodynamic signature of binding. The ITC data also showed that although the copper ion alone hardly contributes to affinity, substrate binding is enhanced for metal-loaded enzymes that are supplied with cyanide, a mimic of O-2(-). Studies with CDH and its isolated heme b cytochrome domain unambiguously showed that the cytochrome domain of CDH interacts with the copper site of the LPMO and that substrate binding precludes interaction with CDH. Apart from providing insights into enzyme-substrate interactions in LPMOs, the present observations shed new light on possible mechanisms for electron supply during LPMO action.

Keywords

lytic polysaccharide monooxygenase; LPMO; cellulose; xyloglucan; cellobiose dehydrogenase

Published in

Proceedings of the National Academy of Sciences
2016, Volume: 113, number: 21, pages: 5922-5927
Publisher: NATL ACAD SCIENCES

    SLU Authors

    • Dimarogona, Maria

      • The Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences

      • Sandgren, Mats

        • The Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences

      UKÄ Subject classification

      Biophysics
      Structural Biology
      Analytical Chemistry
      Biochemistry and Molecular Biology

      Publication Identifiers

      DOI: https://doi.org/10.1073/pnas.1602566113

      Permanent link to this page (URI)

      https://res.slu.se/id/publ/79374