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Inhibition by trimethylamine of methylamine oxidation by Paracoccus denitrificans and bacterium W3A1
1Department of Biochemistry, University of Mississippi Medical Center, Jackson 39216-4505.
Abstract:
Trimethylamine, a common substrate for methylotrophic growth, specifically inhibited methylamine-dependent respiration by Paracoccus denitrificans and bacterium W3A1. These effects were caused by the specific inhibition by trimethylamine of the periplasmic quinoprotein methylamine dehydrogenase. Steady-state kinetic analysis of the effect of trimethylamine on methylamine oxidation by methylamine dehydrogenase indicated that the inhibition was a mixed type. Apparent Ki values for trimethylamine of 1.1 mM and 4.7 mM, respectively, were obtained for the P. denitrificans and bacterium W3A1 enzymes. Methylamine-dependent oxygen consumption by each bacterium was inhibited either by preincubation of cells with trimethylamine prior to the addition of substrate or by addition of trimethylamine to actively respiring cells. Formate-dependent respiration was not inhibited by trimethylamine. A scheme is proposed which describes a regulatory role for trimethylamine in the metabolism and dissimilation of methylamine by methylotrophic bacteria.
Insights
Trimethylamine specifically inhibits methylamine respiration in methylotrophic bacteria by blocking the methylamine dehydrogenase enzyme. This finding suggests trimethylamine plays a regulatory role in methylamine metabolism.
Area of Science:
- Microbiology
- Biochemistry
Background:
- Methylotrophic bacteria utilize simple carbon compounds like methylamine for growth.
- Methylamine metabolism is crucial for these microorganisms, influencing respiration and energy production.
Purpose of the Study:
- To investigate the inhibitory effect of trimethylamine on methylamine respiration in Paracoccus denitrificans and bacterium W3A1.
- To elucidate the mechanism by which trimethylamine affects methylamine metabolism.
Main Methods:
- Enzyme kinetics studies using steady-state analysis to determine inhibition type and constants.
- Respiration assays measuring oxygen consumption in response to methylamine and trimethylamine.
Main Results:
- Trimethylamine was found to be a specific inhibitor of methylamine-dependent respiration.
- The periplasmic enzyme methylamine dehydrogenase was identified as the target of trimethylamine inhibition, exhibiting mixed-type inhibition.
- Apparent inhibition constants (Ki) for trimethylamine were determined for both bacterial species.
Conclusions:
- Trimethylamine acts as a specific inhibitor of methylamine dehydrogenase, impacting methylamine respiration in methylotrophic bacteria.
- A regulatory role for trimethylamine in methylamine metabolism and dissimilation is proposed for these bacteria.