Structural and biochemical studies of the glucuronoyl esterase OtCE15A illuminate its interaction with lignocellulosic components
Journal article, 2019

Glucuronoyl esterases (GEs) catalyze the cleavage of ester linkages between lignin and glucuronic acid moieties on glucuronoxylan in plant biomass. As such, GEs represent promising biochemical tools in industrial processing of these chemically recalcitrant materials. However, details on how GEs interact and catalyze degradation of their natural substrates are sparse, calling for thorough enzyme structure–function studies. GEs belong to carbohydrate esterase family 15 (CE15), which is part of the larger α/β hydrolase superfamily. We present here a structural and mechanistic investigation of the bacterial GE OtCE15A. GEs contain a Ser–His–Asp/Glu catalytic triad, but the location of the catalytic acid in GEs is known to be variable, and OtCE15A possesses two putative catalytic acidic residues in its active site. Through site-directed mutagenesis, we demonstrate here that these residues are functionally redundant, possibly indicating the evolutionary route toward new functionalities within the CE15 family. Structures determined with the bound products glucuronate and galacturonate, as well as a covalently bound intermediate, provided insights into the catalytic mechanism of CE15. A structure of OtCE15A with the glucuronoxylooligosaccharide 23-(4-O-methyl-α-D-glucuronyl)-xylotriose (XUX) disclosed that the enzyme can indeed interact with polysaccharides from the plant cell wall, and an additional structure with the disaccharide xylobiose revealed an enzyme surface binding site that might indicate a mechanism by which the enzyme recognizes long glucuronoxylan chains. These results indicate that OtCE15A, and likely most CE15 family enzymes, can utilize glucuronoxylooligosaccharide esters and support the proposal that these enzymes are active on lignin–carbohydrate complexes in plant biomass.

catalytic triad

cell wall

enzyme kinetics

carbohydrate processing

alpha/beta-hydrolase

lignin-carbohydrate complexes

glucuronoyl esterase

enzyme mutation

carbohydrate-active enzymes

enzyme structure

Author

Scott Mazurkewich

Wallenberg Wood Science Center (WWSC)

Chalmers, Biology and Biological Engineering, Industrial Biotechnology

Jens-Christian N Poulsen

University of Copenhagen

Leila Lo Leggio

University of Copenhagen

Johan Larsbrink

Wallenberg Wood Science Center (WWSC)

Chalmers, Biology and Biological Engineering, Industrial Biotechnology

Journal of Biological Chemistry

0021-9258 (ISSN) 1083-351X (eISSN)

Vol. 294 52 19978-19987

Structure-based engineering of glucuronoyl esterases for separation of lignin and carbohydrates

Novo Nordisk Fonden, 2018-01-01 -- 2020-12-31.

Enzymes for selective decomposition of woody biomass

Knut and Alice Wallenberg Foundation, 2014-01-01 -- 2018-12-31.

Driving Forces

Sustainable development

Subject Categories

Biochemistry and Molecular Biology

Structural Biology

Biocatalysis and Enzyme Technology

Areas of Advance

Energy

Life Science Engineering (2010-2018)

Roots

Basic sciences

DOI

10.1074/jbc.RA119.011435

PubMed

31740581

More information

Latest update

5/11/2020