TY - JOUR

T1 - Structural and functional investigation of a fungal member of carbohydrate esterase family 15 with potential specificity for rare xylans

AU - Mazurkewich, Scott

AU - Scholzen, Karoline C.

AU - Brusch, Rikke H.

AU - Poulsen, Jens Christian N.

AU - Theibich, Yusuf

AU - Hüttner, Silvia

AU - Olsson, Lisbeth

AU - Larsbrink, Johan

AU - Lo Leggio, Leila

N1 - Publisher Copyright: open access.

PY - 2023

Y1 - 2023

N2 - In plant cell walls, covalent bonds between polysaccharides and lignin increase recalcitrance to degradation. Ester bonds are known to exist between glucuronic acid moieties on glucuronoxylan and lignin, and these can be cleaved by glucuronoyl esterases (GEs) from carbohydrate esterase family 15 (CE15). GEs are found in both bacteria and fungi, and some microorganisms also encode multiple GEs, although the reason for this is still not fully clear. The fungus Lentithecium fluviatile encodes three CE15 enzymes, of which two have previously been heterologously produced, although neither was active on the tested model substrate. Here, one of these, LfCE15C, has been investigated in detail using a range of model and natural substrates and its structure has been solved using X-ray crystallography. No activity could be verified on any tested substrate, but biophysical assays indicate an ability to bind to complex carbohydrate ligands. The structure further suggests that this enzyme, which possesses an intact catalytic triad, might be able to bind and act on more extensively decorated xylan chains than has been reported for other CE15 members. It is speculated that rare glucuronoxylans decorated at the glucuronic acid moiety may be the true targets of LfCE15C and other CE15 family members with similar sequence characteristics.

AB - In plant cell walls, covalent bonds between polysaccharides and lignin increase recalcitrance to degradation. Ester bonds are known to exist between glucuronic acid moieties on glucuronoxylan and lignin, and these can be cleaved by glucuronoyl esterases (GEs) from carbohydrate esterase family 15 (CE15). GEs are found in both bacteria and fungi, and some microorganisms also encode multiple GEs, although the reason for this is still not fully clear. The fungus Lentithecium fluviatile encodes three CE15 enzymes, of which two have previously been heterologously produced, although neither was active on the tested model substrate. Here, one of these, LfCE15C, has been investigated in detail using a range of model and natural substrates and its structure has been solved using X-ray crystallography. No activity could be verified on any tested substrate, but biophysical assays indicate an ability to bind to complex carbohydrate ligands. The structure further suggests that this enzyme, which possesses an intact catalytic triad, might be able to bind and act on more extensively decorated xylan chains than has been reported for other CE15 members. It is speculated that rare glucuronoxylans decorated at the glucuronic acid moiety may be the true targets of LfCE15C and other CE15 family members with similar sequence characteristics.

KW - biomass conversion

KW - glucuronyl esterases

KW - hemicellulose

KW - Lentithecium fluviatile

KW - lignocellulose degradation

KW - rare xylans

KW - α/β hydrolases

U2 - 10.1107/S205979832300325X

DO - 10.1107/S205979832300325X

M3 - Journal article

C2 - 37227091

AN - SCOPUS:85160964902

VL - 79

SP - 545

EP - 555

JO - Acta Crystallographica Section D: Structural Biology

JF - Acta Crystallographica Section D: Structural Biology

SN - 2059-7983

IS - 6

ER -