Principles of Biochemistry, Volume 2 - A. Lehninger 1985

Bioenergetics and Metabolism
Biosynthesis of Amino Acids and Nucleotides
Tyrosine is synthesized from the essential amino acid phenylalanine.

Tyrosine is a non-essential amino acid, but in animals it is synthesized from the essential amino acid phenylalanine via hydroxylation of the phenyl group at the 4-position; this reaction is catalyzed by phenylalanine 4-monooxygenase, which also participates in the degradation of phenylalanine (Section 19.5). NADPH serves as the co reductant for the oxygen molecule in this reaction; recall that phenylalanine 4-monooxygenase belongs to the Monooxygenases, or mixed-function oxidases (Section 17.25). The reaction is described by the following equation:

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Last update: 06/08/2026

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