 PNMT catalyzes the transfer of a methyl group from SAM to norepinephrine, converting it into epinephrine.It works by bringing the cofactor SAM and substrate together in close proximity, so that the reactive methyl group can be attacked by the primary amine of the norepinephrine molecule or another catecholamine substrate.The methyl group of SAM is very reactive, so the structure and placement of both norepinephrine and SAM is crucial for correct methylation pattern on the product.