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Auxiliary Activity Family 14

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Auxiliary Activity Family AA14
Clan Structurally related to AA9
Mechanism lytic oxidase
Active site residues mononuclear copper ion
CAZy DB link
http://www.cazy.org/AA14.html


Substrate specificities

The gene encoding the first AA14 family member was identified by analysing transcriptomic and proteomic data from the white-rot basidiomycete Pycnoporus coccineus [1]. This gene was highly upregulated when the fungus was grown on pine or poplar. The corresponding protein (GenBank ID KY769370) was secreted only during growth on pine and poplar, suggesting a role in wood decay. AA14 modules never occur with CBMs, carbohydrate-binding modules which explains why the family could not be discovered by the module-walking approach, as were AA11 and AA13.

The only two AA14 characterized so far were tested for copper dependant oxidase activity on a range of polysaccharides. No activity could be detected on any substrate tested, including cellulose and xylans. However, addition of either of the AA14 enzymes to a Trichoderma reesei cocktail composed of mainly cellulases and xylanases led to a boost of glucose release from poplar and pine . This improvement in glucose release was dose dependent, yielding up to ~100% increase on pretreated softwood. AA14 enzymes also showed synergystic action on wood with AA9 LPMOs. Finally, activity was detected on xylan adsorbed onto cellulose chains, using solid state 13C CP/MAS NMR and mass spectrometry. The observed products were C1 oxidized species with an aldonic acid at the reducing end.

Kinetics and Mechanism

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Catalytic Residues

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Three-dimensional structures

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Family Firsts

First family member identified
AA14 from Pycnoporus coccineus [2].
First demonstration of oxidative cleavage
PcAA114A and PcAA114AB were shown to oxidatively cleave xylan chains bound to cellulose [2].
First 3-D structure
PcAA14B from P. coccineus 5NO7 [2]

References

  1. Couturier M, Navarro D, Chevret D, Henrissat B, Piumi F, Ruiz-Dueñas FJ, Martinez AT, Grigoriev IV, Riley R, Lipzen A, Berrin JG, Master ER, and Rosso MN. (2015) Enhanced degradation of softwood versus hardwood by the white-rot fungus Pycnoporus coccineus. Biotechnol Biofuels. 8, 216. DOI:10.1186/s13068-015-0407-8 | PubMed ID:26692083 | HubMed [Couturier2015]
  2. Couturier M, Ladevèze S, Sulzenbacher G, Ciano L, Fanuel M, Moreau C, Villares A, Cathala B, Chaspoul F, Frandsen KE, Labourel A, Herpoël-Gimbert I, Grisel S, Haon M, Lenfant N, Rogniaux H, Ropartz D, Davies GJ, Rosso MN, Walton PH, Henrissat B, and Berrin JG. (2018) Lytic xylan oxidases from wood-decay fungi unlock biomass degradation. Nat Chem Biol. 14, 306-310. DOI:10.1038/nchembio.2558 | PubMed ID:29377002 | HubMed [Couturier2018]
All Medline abstracts: PubMed | HubMed