What is the function of the enzyme Phenylethanolamine N-methyltransferase?
Phenylethanolamine N-methyltransferase (PNMT) is a critical enzyme in catecholamine synthesis. It transfers the methyl group of S-adenosylmethionine (SAM) to catalyze the synthesis of epinephrine from norepinephrine.
Where is Phenylethanolamine N-methyltransferase found?
adrenal medulla
Phenylethanolamine N-methyltransferase (PNMT; EC 2.1. 1.28) catalyzes the synthesis of epinephrine from norepinephrine, the last step of catecholamine biosynthesis. The enzyme is found predominantly in chromaffin cells of the adrenal medulla, in which epinephrine is synthesized as a hormone.
What converts norepinephrine to epinephrine?
The enzyme phenylethanolamine-N-methyl transferase (PNMT) converts norepinephrine (NE) to epinephrine (E), and cathechol-O-methyl transferase (COMT) and monoamine oxidase (MAO) both metabolize NE and E.
Where is adrenaline Synthesised?
Adrenaline is synthesized in the chromaffin cells of the adrenal medulla of the adrenal gland and a small number of neurons in the medulla oblongata in the brain through a metabolic pathway that converts the amino acids phenylalanine and tyrosine into a series of metabolic intermediates and, ultimately, adrenaline.
Is norepinephrine a protein?
Amino acid-derived hormones are relatively small molecules and include the adrenal hormones epinephrine and norepinephrine. Peptide hormones are polypeptide chains or proteins and include the pituitary hormones, antidiuretic hormone (vasopressin), and oxytocin.
What is epinephrine metabolized by?
Epinephrine is metabolized by the enzymes monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT) as well as by alcohol and aldehyde dehydrogenases Eisenhofer et al (2004).
How does phenylethanolamine N-methyltransferase ( PNMT ) work in the adrenal medulla?
Phenylethanolamine N-methyltransferase (PNMT) is the enzyme that catalyzes the transfer of a methyl group from S-adenosyl-L-methionine (SAM) to norepinephrine in the final step of the biosynthesis of epinephrine. The enzyme has been isolated and purified from the adrenal medulla, where it is localized.
How is PNMT different from other N-methyltransferases?
The enzyme has modest substrate specificity and will transfer methyl groups to the nitrogen atom on a variety of beta-hydroxylated amines. However, adrenal and brain PNMT are distinct from nonspecific N -methyltransferases found in the lung, which can methylate indoleamines such as serotonin.
How does PNMT affect the formation of epinephrine?
The increased levels of epinephrine under stress conditions appear to be in part because of increased PNMT activity. A specific inhibitor of PNMT in the adrenal medulla could suppress the formation of epinephrine without directly interfering with the biosynthesis of other catecholamines.