Indoleamine 2,3-dioxygenase: Antioxidant enzyme in the human eye
- 62 Downloads
• 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.
KeywordsKynurenine Indoleamine Human Lens Lens Protein Body Extract
Unable to display preview. Download preview PDF.
- 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