Protocatechuate 3, 4-dioxygenase from Acinetobacter calcoaceticus

Area of Science:

• Biochemistry
• Enzymology
• Microbial Metabolism

Background:

• Protocatechuate 3,4-dioxygenase (PCD) is crucial for aromatic compound degradation.
• Previous studies focused on PCD from Pseudomonas species.

Purpose of the Study:

• To purify and characterize PCD from Acinetobacter calcoaceticus.
• To compare Acinetobacter PCD with the well-characterized Pseudomonas PCD.

Main Methods:

• Enzyme purification using heat treatment, protamine sulfate, ammonium sulfate fractionation, and column chromatography (DEAE-cellulose, Sephadex G-200).
• Homogeneity assessed by ultracentrifugation and acrylamide gel electrophoresis.
• Comparative analysis including molecular weight, size, iron content, enzyme activity, spectral analysis (visible, circular dichroism), inhibitor studies, and amino acid analysis.

Main Results:

• Successfully purified homogeneous PCD from Acinetobacter calcoaceticus.
• Acinetobacter PCD shares similarities in molecular weight, size, and iron content with Pseudomonas PCD.
• Acinetobacter PCD exhibits lower specific activity and distinct conformational properties compared to Pseudomonas PCD.
• Differential inhibition by protocatechualdehyde and p-hydroxymercuribenzoate observed.
• Amino acid composition analysis revealed significant differences, particularly in proline, methionine, lysine, glutamic acid, and isoleucine content.

Conclusions:

• This is the first report of purified Acinetobacter PCD, revealing its unique characteristics.
• Conformational and active site differences contribute to the functional variations between Acinetobacter and Pseudomonas PCD.
• Further studies on active center conformation are warranted.