Formate dehydrogenase from Pseudomonas oxalaticus.

Area of Science:

• Biochemistry
• Enzymology
• Microbial Physiology

Background:

• Formate dehydrogenase (EC 1.2.1.2) is a key enzyme in microbial metabolism.
• Pseudomonas oxalaticus utilizes formate as a carbon source, necessitating efficient formate dehydrogenase activity.

Purpose of the Study:

• To isolate and characterize formate dehydrogenase from Pseudomonas oxalaticus.
• To investigate the enzyme's composition, catalytic properties, and subunit structure.
• To explore the role of flavin mononucleotide (FMN) in enzyme activity.

Main Methods:

• Enzyme isolation and purification using sucrose gradient centrifugation.
• Biochemical characterization including molecular weight determination.
• Spectroscopic and activity assays to determine cofactor requirements and substrate specificity.

Main Results:

• Isolated enzyme is a flavoprotein (MW 315,000) with FMN, non-heme iron, and acid-labile sulfides.
• A second catalytically active species, a dimer, was observed upon dissociation.
• The enzyme exhibits specificity for formate and transfers electrons to various acceptors, including NAD+ and oxygen.
• Reversible removal and reincorporation of FMN were demonstrated, with formate activity being FMN-dependent.

Conclusions:

• Formate dehydrogenase from P. oxalaticus is a complex flavoprotein with a dimeric structure.
• Flavin mononucleotide (FMN) is essential for the enzyme's specific activity towards formate.
• The enzyme's catalytic versatility extends to non-physiological electron acceptors.