Dopamine degradation catalyzed by MAO and COMT. Dopamine oxidation to aminochrome is prevented by dopamine degradation mediated by both MAO and COMT. MAO catalyzes the oxidative deamination of dopamine amino group to 3,4-dihydroxyphenylacetaldehyde, that is converted to 3,4-dihydroxyphenylacetic acid (DOPAC) catalyzed by aldehyde dehydrogenase. COMT catalyzes the methylation of dopamine to 3-methoxytyramine that is substrate for MAO that catalyzes the formation of 3-metoxy-4-hydroxyphenylacetaldehyde. Homovanillic acid is formed when MAO uses 3-metoxy-4-hydroxyphenylacetaldehyde as substrate or when DOPAC is metabolized by COMT.
