Tyrosine aminotransferase is involved in the oxidative stress response by metabolizing tyrosine in .

Under oxidative stress conditions, hydroxyl radicals can oxidize the phenyl ring of phenylalanine, producing the abnormal tyrosine isomer tyrosine (-tyrosine). Tyrosine levels are commonly used as a biomarker of oxidative stress, and its accumulation has recently been reported to adversely affect cells, suggesting a direct role for tyrosine in oxidative stress effects. We found that the ortholog of tyrosine aminotransferase (TATN-1)-the first enzyme involved in the metabolic degradation of tyrosine-is up-regulated in response to oxidative stress and directly activated by the oxidative stress-responsive transcription factor SKN-1.

Roles of the tyrosine isomers meta-tyrosine and ortho-tyrosine in oxidative stress.

The damage to cellular components by reactive oxygen species, termed oxidative stress, both increases with age and likely contributes to age-related diseases including Alzheimer's disease, atherosclerosis, diabetes, and cataract formation. In the setting of oxidative stress, hydroxyl radicals can oxidize the benzyl ring of the amino acid phenylalanine, which then produces the abnormal tyrosine isomers meta-tyrosine or ortho-tyrosine. While elevations in m-tyrosine and o-tyrosine concentrations have been used as a biological marker of oxidative stress, there is emerging evidence from bacterial, plant, and mammalian studies demonstrating that these isomers, particularly m-tyrosine, directly produce adverse effects to cells and tissues.