Phenylalanine is converted into tyrosine, which is further converted into DOPA by tyrosine hydroxylase with tetrahydropteridine as cofactor. DOPA is decarboxylated to dopamine by a decarboxylase, which is present in many tissues, including a drenal medulla with pyridoxal phosphate as cofactor. The hydroxylation of dopamine is carried out by dopamine β-hydroxylase to form norepinephrine in the presence of ascorbic acid and molecular oxygen. The methylation from methionine converts norepinephrine to epinephrine.