Two o-type oxidases in Methylobacillus flagellatum KT

Area of Science:

• Microbiology
• Biochemistry
• Enzymology

Background:

• Obligate methylotrophs like Methylobacillus flagellatum KT are crucial in methanol metabolism.
• Membrane-bound oxidases play a vital role in microbial respiration and energy production.
• Understanding enzyme kinetics and expression provides insights into bacterial adaptation.

Purpose of the Study:

• To distinguish and characterize o-type oxidases in Methylobacillus flagellatum KT membranes.
• To investigate the influence of growth phases on oxidase expression and activity.
• To elucidate the kinetic properties and inhibitor sensitivities of these enzymes.

Main Methods:

• Laser flash-induced optical absorbance changes were used to study CO-oxidase complexes.
• Kinetic analysis of CO recombination was performed under reducing conditions.
• Inhibition assays with KCN were conducted to determine enzyme sensitivity.

Main Results:

• Two o-type oxidases were distinguished based on KCN sensitivity and CO recombination kinetics.
• One oxidase, similar to Escherichia coli o-type, showed high KCN sensitivity (Ki = 1 microM) and monophasic kinetics.
• The second oxidase, resembling Bacillus sp. FTU o-type, exhibited lower KCN sensitivity (Ki = 6 microM) and three-phasic kinetics.
• Oxidase abundance varied significantly between early exponential and stationary growth phases.

Conclusions:

• Methylobacillus flagellatum KT possesses at least two distinct o-type oxidases with differential kinetic properties and growth-phase-dependent expression.
• These findings contribute to understanding the respiratory chain diversity in methylotrophic bacteria.
• The study highlights the adaptability of bacterial metabolism through differential enzyme expression.