3-O-Methyldopa Unit Converter

3-O-Methyldopa (3-OMD) is a metabolite of L-DOPA, the amino acid precursor to dopamine. It is formed when the enzyme catechol-O-methyltransferase (COMT) methylates L-DOPA instead of L-DOPA being converted into dopamine by aromatic L-amino acid decarboxylase (AADC).

Measuring 3-OMD in plasma helps evaluate catecholamine metabolism. It is used to screen for aromatic L-amino acid decarboxylase (AADC) deficiency, aid in the diagnosis of certain catecholamine-producing tumors such as neuroblastoma, and monitor the effectiveness of levodopa therapy in Parkinson's disease.

3-OMD has a plasma half-life of approximately 15 hours, much longer than L-DOPA's roughly 1-hour half-life. This causes it to accumulate with repeated exposure, making it a useful marker for assessing how much L-DOPA is being diverted away from dopamine production.

3-OMD is produced wherever COMT acts on L-DOPA. The highest COMT activity is found in the liver, followed by the kidneys and gastrointestinal tract. Membrane-bound COMT in the brain also contributes, particularly in the prefrontal cortex and hippocampus.