Brevibacterium fuscum protocatechuate 3,4-dioxygenase. Purification, crystallization, and characterization

Area of Science:

• Biochemistry
• Enzymology
• Spectroscopy

Background:

• Protocatechuate 3,4-dioxygenase enzymes are crucial for aromatic compound degradation.
• Characterization of enzymes from Gram-positive bacteria is less common than from Gram-negative organisms.

Purpose of the Study:

• To purify and characterize a novel protocatechuate 3,4-dioxygenase from Brevibacterium fuscum.
• To investigate its unique spectral features and subunit composition.
• To compare its properties with enzymes from Gram-negative sources.

Main Methods:

• Enzyme purification and crystallization.
• Electron Paramagnetic Resonance (EPR) and Mössbauer spectroscopy.
• Resonance Raman and optical spectroscopy.
• Amino acid analysis and kinetic parameter determination.

Main Results:

• Purified enzyme exhibits exceptionally sharp spectral features, indicating high homogeneity around the Fe site.
• The enzyme has a novel subunit composition: (alpha beta Fe)5.
• Kinetic parameters (Km and turnover number) are significantly higher than those of related enzymes.
• Spectra of the anaerobic protocatechuate complex reveal multiple species with varying electronic symmetries.

Conclusions:

• The Brevibacterium fuscum enzyme represents a unique protocatechuate 3,4-dioxygenase with distinct structural and spectral characteristics.
• Its enhanced kinetic efficiency and sharp spectral features make it an excellent model for mechanistic investigations.
• The absence of cysteine suggests alternative ligands for the iron center.