Comparison of Six Lytic Polysaccharide Monooxygenases from Thermothielavioides terrestris Shows That Functional Variation Underlies the Multiplicity of LPMO Genes in Filamentous Fungi
Journal article, 2022

Lytic polysaccharide monooxygenases (LPMOs) are mono-copper enzymes that oxidatively degrade various polysaccharides. Genes encoding LPMOs in the AA9 family are abundant in filamentous fungi while their multiplicity remains elusive. We describe a detailed functional characterization of six AA9 LPMOs from the ascomycetous fungus Thermothielavioides terrestris LPH172 (syn. Thielavia terrestris). These six LPMOs were shown to be upregulated during growth on different lignocellulosic substrates in our previous study. Here, we produced them heterologously in Pichia pastoris and tested their activity on various model and native plant cell wall substrates. All six T. terrestris AA9 (TtAA9) LPMOs produced hydrogen peroxide in the absence of polysaccharide substrate and displayed peroxidase-like activity on a model substrate, yet only five of them were active on selected cellulosic substrates. TtLPMO9A and TtLPMO9E were also active on birch acetylated glucuronoxylan, but only when the xylan was combined with phosphoric acid-swollen cellulose (PASC). Another of the six AA9s, TtLPMO9G, was active on spruce arabinoglucuronoxylan mixed with PASC. TtLPMO9A, TtLPMO9E, TtLPMO9G, and TtLPMO9T could degrade tamarind xyloglucan and, with the exception of TtLPMO9T, beechwood xylan when combined with PASC. Interestingly, none of the tested enzymes were active on wheat arabinoxylan, konjac glucomannan, acetylated spruce galactoglucomannan, or cellopentaose. Overall, these functional analyses support the hypothesis that the multiplicity of the fungal LPMO genes assessed in this study relates to the complex and recalcitrant structure of lignocellulosic biomass. Our study also highlights the importance of using native substrates in functional characterization of LPMOs, as we were able to demonstrate distinct, previously unreported xylan-degrading activities of AA9 LPMOs using such substrates.

xylan

plant cell wall

biomass degradation

LPMO

filamentous fungi

Thielavia terrestris

Thermothielavioides terrestris

AA9

cellulose

hemicellulose

lytic polysaccharide monooxygenases

Author

Monika Tõlgo

Chalmers, Biology and Biological Engineering, Industrial Biotechnology

Wallenberg Wood Science Center (WWSC)

Olav A. Hegnar

Norwegian University of Life Sciences

Heidi Østby

Norwegian University of Life Sciences

Anikó Várnai

Norwegian University of Life Sciences

francisco Vilaplana

Royal Institute of Technology (KTH)

V. Eijsink

Norwegian University of Life Sciences

Lisbeth Olsson

Wallenberg Wood Science Center (WWSC)

Chalmers, Biology and Biological Engineering, Industrial Biotechnology

Applied and Environmental Microbiology

0099-2240 (ISSN) 1098-5336 (eISSN)

Vol. 88 6 e00096-22

Subject Categories

Biochemistry and Molecular Biology

Microbiology

Biocatalysis and Enzyme Technology

DOI

10.1128/aem.00096-22

More information

Latest update

4/13/2022