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l-DOPA is produced from the amino acid l-tyrosine by the enzyme tyrosine hydroxylase. l-DOPA can act as an l-tyrosine mimetic and be incorporated into proteins by mammalian cells in place of l-tyrosine, generating protease-resistant and aggregate-prone proteins in vitro and may contribute to neurotoxicity with chronic l-DOPA administration. [10]
Phenylalanine hydroxylase catalyzes the conversion of L-phenylalanine to L-tyrosine. Tyrosine hydroxylase catalyzes the rate-limiting step in catecholamine biosynthesis: the conversion of L-tyrosine to L-DOPA. Similarly, tryptophan hydroxylase catalyzes the rate-limiting step in serotonin biosynthesis: the conversion of L-tryptophan to 5 ...
Tyrosine hydroxylase or tyrosine 3-monooxygenase is the enzyme responsible for catalyzing the conversion of the amino acid L-tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA). [5] [6] It does so using molecular oxygen (O 2), as well as iron (Fe 2+) and tetrahydrobiopterin as cofactors.
Phenylalanine hydroxylase (PAH) (EC 1.14.16.1) is an enzyme that catalyzes the hydroxylation of the aromatic side-chain of phenylalanine to generate tyrosine.PAH is one of three members of the biopterin-dependent aromatic amino acid hydroxylases, a class of monooxygenase that uses tetrahydrobiopterin (BH 4, a pteridine cofactor) and a non-heme iron for catalysis.
In humans, catecholamines (shown in yellow) are derived from the amino acid L-phenylalanine. L-Phenylalanine is converted into L-tyrosine by an aromatic amino acid hydroxylase (AAAH) enzyme (phenylalanine 4-hydroxylase), with molecular oxygen (O 2) and tetrahydrobiopterin as cofactors. L-Tyrosine is converted into L-DOPA by another AAAH enzyme ...
Aromatic L-amino acid decarboxylase is active as a homodimer.Before addition of the pyridoxal phosphate cofactor, the apoenzyme exists in an open conformation. Upon cofactor binding, a large structural transformation occurs as the subunits pull closer and close the active site.
d-DOPA (D-3,4-dihydroxyphenylalanine; dextrodopa) is similar to L-DOPA (levodopa), but with opposite chirality. Levo - and dextro - rotation refer to a molecule's ability to rotate planes of polarized light in one or the other direction.
The enzyme 3,4-dihydroxyphenylalanine reductive deaminase (EC 4.3.1.22, reductive deaminase, DOPA-reductive deaminase, DOPARDA; systematic name 3,4-dihydroxy-L-phenylalanine ammonia-lyase (3,4-dihydroxyphenylpropanoate-forming)) [1] catalyses the following chemical reaction