Indoleamine 2,3-dioxygenase: Antioxidant enzyme in the human eye
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• Background: Indoleamine 2,3-dioxygenase (IDO) is the first enzyme of the tryptophan degradation pathway. IDO is an antioxidant enzyme because it is a direct scavenger of superoxide radicals. In this study, we measured the activity of IDO in the human eye. • Methods: IDO was detected in the protein extract of human retina, iris/ciliary body, and lens. The products formed were measured using HPLC with electrochemical detection. Enzyme activity was expressed as the quantity of kynurenine and 3-hydroxykynurenine formed. • Results: IDO activity in the retina extract was 51.5 (± 10) nmol/g tissue/h, and kynurenine formation was detected. In the iris/ciliary body, IDO activity was 191.8 (±49) nmol/g tissue/h, and both kynurenine and 3-hydroxy-kynurenine were formed from tryptophan. In the extract of lens cortex only 3-hydroxykynurenine was formed from tryptophan. IDO activity was 351 (±67.3) nmol/g tissue/h. • Conclusion: Free tryptophan is degradated in the human eye by IDO, an antioxidative enzyme. IDO may be an antioxidant mechanism in the eye.
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- 8.Lerman S, Forbes WF, Zigman S (1967) The effect of aging irradiation on the thiol content of the soluble lens proteins. Invest Ophthalmol Vis Sci 6: 552–553Google Scholar
- 12.Planck SR, Huang XN, Robertson EJ, Rosenbaum JT (1993) Cytokine mRNA levels in rat ocular tissues following systemic endotoxin treatment. Invest Ophthalmol Vis Sci [Suppl] 34: 1142Google Scholar
- 15.Pitts DG, Cameron LL, Jose JG, Lerman S, Moss E, Varma SD, Zigler Z, Zigman S, Zuclich J (1986) Optical radiation and cataracts. In: Waxler M, Hitchins VM (eds) Optical radiation and visual health. CRC Press, Boca Raton, Florida, pp 5–42Google Scholar
- 19.Van Heyningen R (1973) The human lens — in relation to the cataract. In: Elliott K, Fitzsimons DW (eds) Ciba Foundation Symposium vol. 19. Elsevier, Amsterdam, pp 151–171Google Scholar
- 22.Yamazaki F, Kuroiwa T, Takikawa O, Kido R (1985) Human indolylamine 2,3-dioxygenase. Its tissue distribution and characterization of placental enzyme. Biochem 1230: 635–638Google Scholar