Norepinephrine metabolizing enzymes

The enzymes involved in norepinephrine metabolism in the vein wall, primarily monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT), are critical regulators of venous hemodynamics and vascular tone (Guilhou et al., 1997). These enzymes are responsible for the catabolism of norepinephrine, the primary neurotransmitter that induces venous smooth muscle contraction through the activation of alpha-adrenergic receptors. By modulating the local concentration of norepinephrine at the neuroeffector junction, these enzymes directly influence the degree of venous vasoconstriction and capacitance. In conditions such as chronic venous insufficiency (CVI) and varicose veins, impaired venous tone leads to blood stasis and increased venous pressure. Phlebotonic drugs, such as the micronized purified flavonoid fraction (MPFF) containing diosmin and hesperidin, target these enzymes to inhibit their activity (Cyrino et al., 2004). This inhibition prolongs the presence of norepinephrine, thereby enhancing venous tone, reducing venous distensibility, and improving clinical symptoms associated with venous hypertension (StatPearls, 2023).

Other names

Monoamine oxidaseCatechol-O-methyltransferaseMAOCOMTNorepinephrine-degrading enzymes

Inhibition of enzymatic degradation of norepinephrine (via MAO and COMT inhibition) to prolong vasoconstriction and increase venous tone.