Synthetic esters recognized by glucuronoyl esterase from Schizophyllum commune

Area of Science:

• Biochemistry
• Enzymology
• Wood-rotting fungi

Background:

• A novel carbohydrate esterase, glucuronoyl esterase, was identified in the cellulolytic system of Schizophyllum commune.
• Its initial characterization involved hydrolysis of methyl ester of 4-O-methyl-D-glucuronic acid, but its role in lignin-carbohydrate complex deconstruction remained unclear.

Purpose of the Study:

• To investigate the substrate specificity of glucuronoyl esterase using synthetic compounds mimicking lignin-carbohydrate ester linkages.
• To compare the enzyme's catalytic efficiency on different uronic acid and alcohol moieties.

Main Methods:

• Enzymatic hydrolysis assays using synthetic esters of 4-O-methyl-D-glucuronic acid and D-glucuronic acid with 3-(4-methoxyphenyl)propyl alcohol.
• Kinetic analysis of substrate hydrolysis.
• Enzyme activity assessment on xylooligosaccharides with 4-O-methyl-D-glucopyranuronosyl residues.

Main Results:

• Glucuronoyl esterase effectively hydrolyzed synthetic esters mimicking lignin-carbohydrate ester linkages.
• The enzyme demonstrated higher catalytic efficiency for esters of 4-O-methyl-D-glucuronic acid compared to D-glucuronic acid.
• Enzyme recognition was primarily directed towards the uronic acid component rather than the alcohol moiety.
• The rate of deesterification was independent of the carbohydrate backbone structure.

Conclusions:

• Glucuronoyl esterase plays a role in cleaving ester linkages within lignin-carbohydrate complexes.
• The enzyme exhibits specificity for 4-O-methyl-D-glucuronic acid residues, crucial for understanding plant cell wall degradation.
• Findings provide insights into the enzymatic mechanisms involved in biomass deconstruction by wood-rotting fungi.