Protocatechuate is not metabolized via catechol in Enterobacter aerogenes

Area of Science:

• Microbial metabolism
• Bacterial biochemistry
• Enzyme kinetics

Background:

• Protocatechuate is a common aromatic compound metabolized by bacteria.
• Typically, bacterial protocatechuate metabolism involves oxygenative cleavage to beta-carboxymuconate.
• A proposed alternative pathway in Enterobacter aerogenes involves nonoxidative decarboxylation to catechol.

Purpose of the Study:

• To investigate the metabolic pathway of protocatechuate in Enterobacter aerogenes.
• To determine the significance of the proposed nonoxidative decarboxylation pathway versus the canonical oxygenative cleavage pathway.

Main Methods:

• Construction and analysis of mutant strains of E. aerogenes.
• Assessing protocatechuate utilization in wild-type and mutant strains.
• Monitoring enzyme induction related to protocatechuate and catechol metabolism.

Main Results:

• Mutations affecting catechol metabolism did not impede protocatechuate utilization, indicating the nonoxidative pathway is not significant.
• Enzymes for oxygenative cleavage and further metabolism of protocatechuate were induced during its metabolism.
• Inactivation of the oxygenative pathway genes prevented protocatechuate degradation.
• E. aerogenes exhibited broad inductive control over genes for protocatechuate and catechol metabolism, suggesting multiple metabolite triggers.

Conclusions:

• The primary route for protocatechuate metabolism in E. aerogenes is oxygenative cleavage.
• The proposed nonoxidative decarboxylation pathway plays a minor role, if any.
• Gene expression for protocatechuate metabolism is broadly regulated by various metabolites.