Request a Quote

Monoamine oxidase (MAO) reaction phenotyping assay

Understand if your compound is metabolized by MAO-A or MAO-B enzyme.

Monoamine oxidase (MAO) reaction phenotyping is a non-CYP mediated metabolism assay within our portfolio of in vitro ADME screening services. Cyprotex deliver consistent, high quality data with the flexibility to adapt protocols based on specific customer requirements.

Determining potential metabolism by MAO enzymes

  • Monoamine oxidases (MAO) are membrane-associated enzymes located specifically on the outer mitochondrial membrane. They are the major enzymes participating in the catabolism of monoamine neurotransmitters and related exogenous amines.
  • Two isoforms of MAO exist, MAO-A and MAO-B, which differ in their substrate specificity, inhibitor selectivity and tissue distribution.
  • Selective MAO-A inhibitors are useful in the therapy of depression and anxiety whereas MAO-B inhibitors are often used in the treatment of Parkinson’s and Alzheimer’s diseases.
  • Cyprotex’s MAO reaction phenotyping assay identifies if your compound is a substrate for either MAO-A or MAO-B.
In human brain the predominant form is MAO-B, expressed at highest levels in astrocytes and serotonergic neurons, while MAO-A is expressed at highest levels in catecholaminergic neurons.

1Hotamisligil GS and Breakefield XO (1991) Am J Hum Genet 49(2); 383–392


Monoamine Oxidase (MAO) reaction phenotyping assay protocol

Test System hMAO-A and hMAO-B expressed enzyme
Test Article Concentration 1 µM (different concentrations available)
Time Points 0, 5, 15, 30, 45 min
Negative Control cDNA expressed control preparation (no MAO present)
Positive Control Kynuramine
Test Article Requirements 100 µL of a 10 mM DMSO solution (or equivalent amount in solid)
Analysis method LC-MS/MS
Data Delivery % Parent compound remaining at each time point for each isoform
Half life
Standard error of half life


Data from the monoamine oxidase (MAO) reaction phenotyping assay

Figure 1
Metabolic stability of the MAO substrate, kynuramine over 45 min in the presence of MAO-A and MAO-B expressed enzyme (Each data-point is mean of n=3).


1 Hotamisligil GS and Breakefield XO (1991) Human monoamine oxidase A gene determines levels of enzyme activity. Am J Hum Genet 49(2); 383–392

Learn More

Learn more about drug metabolism in chapter 3 of our popular Everything you need to know about ADME guide. 

Order your copy

ADME guide
Get a Quote
ADME Guide DDI Guide TOX Guide Visit the e-Store
Contact us to discuss your ADME Tox issues or request a quote

Europe: +44 (0)1625 505100
North America (East Coast): +1-888-297-7683

or fill out the form below:


Download file