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[Molecular weight of mitochondrial type B MAO in various organs of guinea pig]
Abstract:
Molecular weights of mitochondrial type B monoamine oxidase (MAO) in guinea pig brain, liver and kidney were estimated, and their identities and multiplicity were studied. We ascertained what concentration of 3H-pargyline bound to type B MAO specifically from the inhibition curve toward serotonin (5-HT) and beta-phenylethylamine (beta-PEA) by pargyline. Pargyline irreversibly binds to FAD in MAO at a one to one molecular ratio. 3H-pargyline bound to type B MAO specifically and irreversibly by incubation for 5 hr at 37 degrees C, and SDS-disc electrophoresis was carried out using 3H-pargyline as a tracer. The molecular weight of MAO was estimated after specific binding of pargyline was corrected for non-specific binding. The molecular weight of type B MAO in every organ was found to be 60,000, giving a single peak after solubilization with 6% SDS, but several peaks at higher molecular weight were found in each organ after solubilization with 2% SDS. In the brain, there appeared to be a peak of 100,000, and it was suggested that the MAO existed as a dimer which was composed of a FAD containing subunit and a low molecular weight subunit containing no FAD. In the liver, there appeared to be peaks of 120,000 and 240,000, and it was suggested that the MAO existed as a dimer and tetramer. In the kidney, there appeared to be a peak of 180,000, and MAO was suggested to exist as a trimer.
Insights
Mitochondrial type B monoamine oxidase (MAO) molecular weights were studied in guinea pig organs. Type B MAO exists as a 60,000 MW monomer, with higher oligomers observed in brain, liver, and kidney.
Area of Science:
- Biochemistry
- Molecular Biology
- Neuroscience
Background:
- Mitochondrial monoamine oxidase (MAO) is crucial for neurotransmitter metabolism.
- Type B MAO specifically metabolizes substrates like beta-phenylethylamine (beta-PEA).
- Understanding MAO's quaternary structure is key to its function and inhibition.
Purpose of the Study:
- To determine the molecular weights of mitochondrial type B MAO in guinea pig brain, liver, and kidney.
- To investigate the potential multiplicity and oligomeric states of type B MAO.
- To characterize the specific binding of the irreversible inhibitor pargyline to type B MAO.
Main Methods:
- Specific binding of 3H-pargyline to type B MAO was determined using inhibition curves with serotonin (5-HT) and beta-phenylethylamine (beta-PEA).
- SDS-polyacrylamide gel electrophoresis (SDS-PAGE) was performed using 3H-pargyline as a tracer.
- Molecular weights were estimated after correcting for non-specific pargyline binding.
Main Results:
- Type B MAO consistently showed a molecular weight of 60,000 in all organs studied, representing a monomeric form.
- Solubilization with 2% SDS revealed higher molecular weight peaks, suggesting oligomerization: 100,000 (dimer) in brain, 120,000 (dimer) and 240,000 (tetramer) in liver, and 180,000 (trimer) in kidney.
- The brain dimer is proposed to consist of a FAD-containing subunit and a non-FAD subunit.
Conclusions:
- Mitochondrial type B MAO exists as a 60,000 MW monomer.
- Oligomeric forms (dimers, trimers, tetramers) of type B MAO are present in different guinea pig organs.
- These findings provide insights into the structural diversity and assembly of MAO B.