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Discovery and characterization of a new family of lytic polysaccharide monooxygenases.

Hemsworth GR, Henrissat B, Davies GJ, Walton PH - Nat. Chem. Biol. (2013)

Bottom Line: They are attracting considerable attention owing to their potential use in biomass conversion, notably in the production of biofuels.Previous studies have identified two discrete sequence-based families of these enzymes termed AA9 (formerly GH61) and AA10 (formerly CBM33).The newly characterized AA11 family expands the LPMO clan, potentially broadening both the range of potential substrates and the types of reactive copper-oxygen species formed at the active site of LPMOs.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of York, Heslington, York, UK.

ABSTRACT
Lytic polysaccharide monooxygenases (LPMOs) are a recently discovered class of enzymes capable of oxidizing recalcitrant polysaccharides. They are attracting considerable attention owing to their potential use in biomass conversion, notably in the production of biofuels. Previous studies have identified two discrete sequence-based families of these enzymes termed AA9 (formerly GH61) and AA10 (formerly CBM33). Here, we report the discovery of a third family of LPMOs. Using a chitin-degrading exemplar from Aspergillus oryzae, we show that the three-dimensional structure of the enzyme shares some features of the previous two classes of LPMOs, including a copper active center featuring the 'histidine brace' active site, but is distinct in terms of its active site details and its EPR spectroscopy. The newly characterized AA11 family expands the LPMO clan, potentially broadening both the range of potential substrates and the types of reactive copper-oxygen species formed at the active site of LPMOs.

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Structure of typical AA9 and active sites of AA9 and AA10. (a) Overall structure of AA9 from Thermoascus aurantiacus5 with the active site copper shown as a sphere and active site residues shown as sticks, (b) schematic representations of the Cu active sites observed in AA9 and AA10 structures.
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Figure 1: Structure of typical AA9 and active sites of AA9 and AA10. (a) Overall structure of AA9 from Thermoascus aurantiacus5 with the active site copper shown as a sphere and active site residues shown as sticks, (b) schematic representations of the Cu active sites observed in AA9 and AA10 structures.

Mentions: LPMOs studied thus far have an active site that is located near the center of an extended flat face, where the face is presumed to interact with the crystalline surface of the substrate (Fig. 1a). Following initial AA98 and AA103 3-D structure solutions, X-ray crystallographic structural details of the Cu-active site were first fully shown in a cellulose-active fungal LPMO from Thermoascus aurantiacus in which a single copper ion is chelated by two nitrogen atoms of the N-terminal histidine (through the NH2 terminus and an N-atom of the side chain) and a further nitrogen atom of another histidine side chain in an overall T-shaped N3 configuration coined as the histidine brace (Fig. 1b).5 It was further demonstrated that additional differences exist between the fungal AA9 and bacterial AA10 versions, where the fungal AA9 enzymes have a tyrosine residue adjacent to the copper coordination sphere and, when expressed in filamentous fungal systems, carry an unusual methylation on the τ-N atom of the N-terminal histidine.9 The methylation is not essential for activity, as non-methylated versions expressed in Pichia pastoris are known to be active,10,11 but its exact role is yet to be defined. In a further refinement, a classification of LPMOs based upon whether the principal site of oxidation is C1 or C4 has been proposed,9 while oxidation at C6 has been proposed for some AA9 LPMOs. 5,10


Discovery and characterization of a new family of lytic polysaccharide monooxygenases.

Hemsworth GR, Henrissat B, Davies GJ, Walton PH - Nat. Chem. Biol. (2013)

Structure of typical AA9 and active sites of AA9 and AA10. (a) Overall structure of AA9 from Thermoascus aurantiacus5 with the active site copper shown as a sphere and active site residues shown as sticks, (b) schematic representations of the Cu active sites observed in AA9 and AA10 structures.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4274766&req=5

Figure 1: Structure of typical AA9 and active sites of AA9 and AA10. (a) Overall structure of AA9 from Thermoascus aurantiacus5 with the active site copper shown as a sphere and active site residues shown as sticks, (b) schematic representations of the Cu active sites observed in AA9 and AA10 structures.
Mentions: LPMOs studied thus far have an active site that is located near the center of an extended flat face, where the face is presumed to interact with the crystalline surface of the substrate (Fig. 1a). Following initial AA98 and AA103 3-D structure solutions, X-ray crystallographic structural details of the Cu-active site were first fully shown in a cellulose-active fungal LPMO from Thermoascus aurantiacus in which a single copper ion is chelated by two nitrogen atoms of the N-terminal histidine (through the NH2 terminus and an N-atom of the side chain) and a further nitrogen atom of another histidine side chain in an overall T-shaped N3 configuration coined as the histidine brace (Fig. 1b).5 It was further demonstrated that additional differences exist between the fungal AA9 and bacterial AA10 versions, where the fungal AA9 enzymes have a tyrosine residue adjacent to the copper coordination sphere and, when expressed in filamentous fungal systems, carry an unusual methylation on the τ-N atom of the N-terminal histidine.9 The methylation is not essential for activity, as non-methylated versions expressed in Pichia pastoris are known to be active,10,11 but its exact role is yet to be defined. In a further refinement, a classification of LPMOs based upon whether the principal site of oxidation is C1 or C4 has been proposed,9 while oxidation at C6 has been proposed for some AA9 LPMOs. 5,10

Bottom Line: They are attracting considerable attention owing to their potential use in biomass conversion, notably in the production of biofuels.Previous studies have identified two discrete sequence-based families of these enzymes termed AA9 (formerly GH61) and AA10 (formerly CBM33).The newly characterized AA11 family expands the LPMO clan, potentially broadening both the range of potential substrates and the types of reactive copper-oxygen species formed at the active site of LPMOs.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of York, Heslington, York, UK.

ABSTRACT
Lytic polysaccharide monooxygenases (LPMOs) are a recently discovered class of enzymes capable of oxidizing recalcitrant polysaccharides. They are attracting considerable attention owing to their potential use in biomass conversion, notably in the production of biofuels. Previous studies have identified two discrete sequence-based families of these enzymes termed AA9 (formerly GH61) and AA10 (formerly CBM33). Here, we report the discovery of a third family of LPMOs. Using a chitin-degrading exemplar from Aspergillus oryzae, we show that the three-dimensional structure of the enzyme shares some features of the previous two classes of LPMOs, including a copper active center featuring the 'histidine brace' active site, but is distinct in terms of its active site details and its EPR spectroscopy. The newly characterized AA11 family expands the LPMO clan, potentially broadening both the range of potential substrates and the types of reactive copper-oxygen species formed at the active site of LPMOs.

Show MeSH
Related in: MedlinePlus