The rate-limiting step for nor-epinephrine synthesis is:
Ref: KD Tripathi Pharmacology 7th edition(page no;125) Catecholamines like epinephrine, norepinephrine, dopamine are synthesized from the amino acid phenylalanine. Tyrosine hydroxylase is the rate-limiting enzyme and its inhibition by alpha-methyl-p-tyrosine results in depletion of norepinephrine Tyrosine hydroxylase helps in Conversion of tyrosine to DOPA
Conversion of phenylalanine to tyrosine
Conversion of tyrosine to DOPA
Conversion of DOPA to dopamine
Conversion of dopamine to norepinephrine
Autonomic nervous system