A bioluminescent assay for monoamine oxidase activity

Area of Science:

• Biochemistry
• Enzymology
• Assay Development

Background:

• Monoamine oxidase (MAO) enzymes play critical roles in neurotransmitter metabolism and are targets for various therapeutic agents.
• Existing methods for MAO activity assessment often lack the sensitivity or throughput required for comprehensive drug screening.
• Identifying novel MAO inhibitors is essential for understanding drug metabolism and developing new pharmaceuticals.

Purpose of the Study:

• To develop and validate a novel, homogeneous, two-step bioluminescent assay for quantifying monoamine oxidase (MAO) activity.
• To assess the assay's suitability for high-throughput screening (HTS) and its sensitivity compared to existing fluorescent methods.
• To evaluate the prevalence of MAO inhibitors within a diverse compound library.

Main Methods:

• A two-step homogeneous bioluminescent assay was designed, utilizing an aminopropylether analog of methyl ester luciferin.
• Step 1 involved the reaction of MAO with the substrate analog.
• Step 2 employed a luciferin detection reagent to quench MAO activity and generate a luminescent signal proportional to MAO levels.

Main Results:

• The bioluminescent assay demonstrated high precision and superior sensitivity compared to fluorescent assays.
• The luminescent signal exhibited stability with a half-life exceeding 5 hours.
• An automated screen of 1280 compounds identified a 16% hit rate for MAO inhibitors with a low false positive rate (0.9%).

Conclusions:

• The developed bioluminescent assay is a simple, sensitive, and HTS-amenable tool for MAO activity measurement.
• The assay accurately determines binding constants for MAO substrates and inhibitors.
• The high prevalence of MAO inhibitors in a compound library underscores the importance of incorporating MAO assays into drug metabolism studies.