Catechol-O-methyltransferase activity in human erythrocytes: methodological aspects

Area of Science:

• Biochemistry
• Enzymology
• Pharmacology

Background:

• Catechol-O-methyltransferase (COMT) is crucial for metabolizing catecholamines.
• Standardized assays are needed for reliable COMT activity measurement in research and clinical settings.

Purpose of the Study:

• To investigate and optimize methodological aspects for assaying human erythrocyte COMT activity.
• To determine optimal conditions for sample collection, storage, and substrate use.

Main Methods:

• Assessed COMT activity in human erythrocytes under various conditions.
• Varied storage temperatures, durations, and sample preparation techniques (lysis, freeze-thawing, sonication).
• Evaluated different substrates (noradrenaline, DBA) and methyl-donor concentrations (SAMe).

Main Results:

• COMT activity showed no significant temporal variations over 24 hours or one month.
• Washed erythrocytes from blood collected with heparin, EDTA, or citrate were suitable enzyme sources.
• Optimal storage involved intact erythrocytes at -85°C for long-term stability (>2 years) or up to one week at +4°C.
• 3,4-dihydroxybenzoic acid (DBA) yielded higher activity and affinity compared to noradrenaline.
• S-adenosyl-1-methionine (SAMe) concentration influenced activity up to 0.1 mM.

Conclusions:

• The optimized erythrocyte COMT assay is reproducible and convenient, requiring minimal blood samples.
• Washing erythrocytes effectively eliminates interference from plasma factors.
• The assay provides a reliable method for measuring COMT activity, essential for catecholamine metabolism studies.