The first step in its degradation is carried out by a mixed-function oxidase using tetrahydrobiopterin.  
The first step in its degradation is carried out by a mixed-function oxidase using tetrahydrobiopterin.  Aspartame has the methyl ester of this amino acid, which is a precursor of (*) dopamine and  norepinephrine and hydroxylated to tyrosine. Donating an amino group to pyruvate, decarboxylated to phenylacetate, or reduced to phenyllactate when its metabolism fails in PKU, for 10 points— name this simplest aromatic amino acid.
The first step in its degradation is carried out by a mixed-function oxidase using tetrahydrobiopterin.  
phenylalanine