Dienelactone hydrolase from Pseudomonas sp. strain B13

Area of Science:

• Biochemistry
• Enzymology
• Microbial Metabolism

Background:

• Dienelactone hydrolase (EC 3.1.1.45) is crucial for converting dienelactone to maleylacetate.
• Pseudomonas sp. strain B13 utilizes 3-chlorobenzoate, implying relevant enzyme activities.
• Understanding hydrolase mechanisms aids in bioremediation and metabolic pathway elucidation.

Purpose of the Study:

• To purify and characterize dienelactone hydrolase from Pseudomonas sp. strain B13.
• To investigate the enzyme's molecular properties, including its active site.
• To compare dienelactone hydrolase with related enzymes, such as enol-lactone hydrolases.

Main Methods:

• Enzyme purification via 24-fold enrichment from bacterial extracts.
• Crystallization and determination of molecular weight (monomer, ~30,000 Da).
• Sulfhydryl group analysis using p-chloromercuribenzoate and dithiothreitol.

Main Results:

• Homogeneous dienelactone hydrolase was obtained, existing as a monomer.
• Two cysteinyl residues were identified; one reactive and essential for activity, the other protected.
• Structural and sequence similarities were found with enol-lactone hydrolases, suggesting common ancestry.
• Dienelactone hydrolase exhibited a kcat of 1,800 min⁻¹, significantly lower than enol-lactone hydrolases.

Conclusions:

• Dienelactone hydrolase shares structural and evolutionary links with enol-lactone hydrolases.
• The enzyme's low catalytic efficiency may necessitate high expression levels in Pseudomonas sp. strain B13.
• Further research into hydrolase function can inform applications in environmental science and biotechnology.