What process results in the formation of metanephrine?

The formation of metanephrine occurs through the metabolism of epinephrine by catechol-O-methyltransferase (COMT). During this process, the enzyme COMT catalyzes the transfer of a methyl group to the hydroxyl group of the catecholamine structure of epinephrine, transforming it into metanephrine. This pathway reflects one of the key mechanisms our body uses to break down catecholamines, ultimately allowing for their elimination and regulation within the body.

The other choices present alternative pathways but refer to different substances or enzymes. Norepinephrine is metabolized by COMT as well, but it produces normetanephrine rather than metanephrine. Additionally, monoamine oxidase (MAO) metabolizes both epinephrine and norepinephrine, but it primarily involves oxidative deamination, which does not produce metanephrine directly. Therefore, the specific involvement of COMT in the methylation of epinephrine highlights why this option specifically leads to the formation of metanephrine.