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The enzyme phenylalanine ammonia lyase (EC 4.3.1.24) catalyzes the conversion of L-phenylalanine to ammonia and trans-cinnamic acid.: [1] L -phenylalanine = trans -cinnamate + NH 3 Phenylalanine ammonia lyase (PAL) is the first and committed step in the phenyl propanoid pathway and is therefore involved in the biosynthesis of the polyphenol ...
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.
Good sources of phenylalanine are eggs, chicken, liver, beef, milk, and soybeans. [7] Another common source of phenylalanine is anything sweetened with the artificial sweetener aspartame, such as diet drinks, diet foods and medication; the metabolism of aspartame produces phenylalanine as one of the compound's metabolites. [8]
In plants, all phenylpropanoids are derived from the amino acids phenylalanine and tyrosine. Phenylalanine ammonia-lyase (PAL, a.k.a. phenylalanine/tyrosine ammonia-lyase) is an enzyme that transforms L-phenylalanine and tyrosine into trans-cinnamic acid and p-coumaric acid, respectively.
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.
So, for convenience, sulfur-containing amino acids are sometimes considered a single pool of nutritionally equivalent amino acids as are the aromatic amino acid pair, phenylalanine and tyrosine. Likewise arginine , ornithine , and citrulline , which are interconvertible by the urea cycle , are considered a single group.
From glycolysis, glucose 6-phosphate is a precursor for histidine; 3-phosphoglycerate is a precursor for glycine and cysteine; phosphoenol pyruvate, combined with the 3-phosphoglycerate-derivative erythrose 4-phosphate, forms tryptophan, phenylalanine, and tyrosine; and pyruvate is a precursor for alanine, valine, leucine, and isoleucine.
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 .