A chlorogenic acid esterase with a unique substrate specificity from Ustilago maydis

Area of Science:

• Enzymology
• Biochemistry
• Molecular Biology

Background:

• Extracellular esterases play crucial roles in breaking down plant biomass.
• Chlorogenic acid esterases are important for processing phenolic compounds.
• Ustilago maydis is a fungal pathogen with potential for producing novel enzymes.

Purpose of the Study:

• To purify and characterize a novel chlorogenic acid esterase from Ustilago maydis (UmChlE).
• To investigate the substrate specificity and kinetic properties of UmChlE.
• To confirm the enzyme's activity on natural plant substrates and explore its gene expression.

Main Methods:

• Enzyme purification using anion-exchange, isoelectric focusing, and affinity/hydrophobic interaction chromatography.
• SDS-PAGE for molecular weight determination.
• Enzyme activity assays across a range of pH and temperatures.
• Kinetic analysis using various ester substrates.
• Gene cloning, expression in Pichia pastoris, and sequence alignment.

Main Results:

• A homogeneous UmChlE monomer (approx. 71 kDa) was obtained, optimal at pH 7.5 and 37°C.
• UmChlE demonstrated broad pH activity (3.5-9.5) and high affinity for chlorogenic acid (Km = 19.6 μM).
• The enzyme exhibited activity on feruloyl esterase substrates and released phenolic acids from wheat bran and coffee pulp.

Conclusions:

• UmChlE is a unique esterase with broad substrate specificity, active on both chlorogenic acid and feruloyl esterase substrates.
• The enzyme effectively degrades complex plant biomass, indicating potential biotechnological applications.
• The gene encoding UmChlE was successfully expressed in Pichia pastoris, and sequence analysis highlighted its distinctiveness.