Search results
Results from the WOW.Com Content Network
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 ball and stick model spinning. Phenylalanine (symbol Phe or F) [3] is an essential α-amino acid with the formula C 9 H 11 NO 2.It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine.
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.
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 ...
In addition to the common amino acid L-tyrosine, which is the para isomer (para-tyr, p-tyr or 4-hydroxyphenylalanine), there are two additional regioisomers, namely meta-tyrosine (also known as 3-hydroxyphenylalanine, L-m-tyrosine, and m-tyr) and ortho-tyrosine (o-tyr or 2-hydroxyphenylalanine), that occur in nature.
Tetrahydrobiopterin is required to convert Phe to Tyr and is required to convert Tyr to L-DOPA via the enzyme tyrosine hydroxylase. L-DOPA, in turn, is converted to dopamine. Low levels of dopamine lead to high levels of prolactin. By contrast, in classical PKU (without dihydrobiopterin involvement), prolactin levels would be relatively normal.
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