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Phenylethanolamine N-methyltransferase (PNMT) is an enzyme found primarily in the adrenal medulla that converts norepinephrine (noradrenaline) to epinephrine (adrenaline). [1] It is also expressed in small groups of neurons in the human brain [ 2 ] and in selected populations of cardiomyocytes .
In appearance, phenylethanolamine is a white solid. Phenylethanolamine is perhaps best known in the field of bioscience as part of the enzyme name "phenylethanolamine N-methyl transferase", referring to an enzyme which is responsible for the conversion of norepinephrine into epinephrine, as well as other related transformations. [3]
Phosphatidylethanolamine N-methyltransferase (abbreviated PEMT) is a transferase enzyme (EC 2.1.1.17) which converts phosphatidylethanolamine (PE) to phosphatidylcholine (PC) in the liver. [5] [6] [7] In humans it is encoded by the PEMT gene within the Smith–Magenis syndrome region on chromosome 17. [8] [9]
These enzymes use S-adenosylmethionine as a methyl donor and contain several highly conserved structural features between the three forms; these include the S-adenosylmethionine binding site, a vicinal proline-cysteine pair which forms a thiolate anion important for the reaction mechanism, and the cytosine substrate binding pocket.
In mammals, phenethylamine is produced from the amino acid L-phenylalanine by the enzyme aromatic L-amino acid decarboxylase via enzymatic decarboxylation. [14] In addition to its presence in mammals, phenethylamine is found in many other organisms and foods, such as chocolate , especially after microbial fermentation .
In still other neurons in which epinephrine is the transmitter, a third enzyme phenylethanolamine N-methyltransferase (PNMT) converts norepinephrine into epinephrine. Thus, a cell that uses epinephrine as its transmitter contains four enzymes (TH, AADC, DBH, and PNMT), whereas norepinephrine neurons contain only three enzymes (lacking PNMT) and ...
N-Methylphenethylamine (NMPEA) is a naturally occurring trace amine neuromodulator in humans that is derived from the trace amine, phenethylamine (PEA). [2] [3] It has been detected in human urine (<1 μg over 24 hours) [4] and is produced by phenylethanolamine N-methyltransferase with phenethylamine as a substrate, which significantly increases PEA's effects.
Dopamine is converted into norepinephrine by the enzyme dopamine β-hydroxylase, with O 2 and L-ascorbic acid as cofactors. [25] Norepinephrine is converted into epinephrine by the enzyme phenylethanolamine N-methyltransferase with S-adenosyl-L-methionine as the cofactor. [25] Some of the cofactors also require their own synthesis. [25]