title: EGCG prevents tryptophan oxidation of cataractous ocular lens human γ-crystallin in presence of H2O2.
abstract: Disruption of the short range order of proteins present in the ocular lens leads to cataract resulting in a loss of transparency. Human γ-crystallin (HGC), a water soluble protein present in the lens is known to aggregate with aging. A modified form of HGC (HGC(c)) was isolated from cataractous human ocular lens extract and the number of Trp residues that undergo oxidation was determined. The extent of oxidized Trp (N-formyl kynurenine) in HGC due to cataract formation was determined, primarily using fluorescence spectroscopy. The ability of (-)-epigallocatechin gallate (EGCG) to retain its antioxidant effect even in the presence of H2O2 was investigated. This was monitored by its ability to prevent the modification of intact Trp residues in HGC(c) isolated from cataractous human eye lens. Significant Trp fluorescence quenching occurs on interaction of the green tea component, EGCG with HGC(c) accompanied by a red shift. Docking studies were employed to substantiate the experimental results. As eye lens proteins are prone to oxidative stress it is essential that a clear understanding of the effects of the components generated in vivo vis-à-vis the antioxidant effects of natural polyphenols be obtained.
authors.affiliation: Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India.
authors.forename: Susmitnarayan
authors.initials: S
authors.lastname: Chaudhury
authors.affiliation: Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India.
authors.forename: Ishita
authors.initials: I
authors.lastname: Ghosh
authors.affiliation: Railway Bungalow No. 305, South Side, Kharagpur 721301, India.
authors.forename: Gautam
authors.initials: G
authors.lastname: Saha
authors.affiliation: Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India. Electronic address: swagata@chem.iitkgp.ernet.in.
authors.forename: Swagata
authors.initials: S
authors.lastname: Dasgupta
mesh_terms: D002386:Cataract / Q000378:metabolism*; D002392:Catechin / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007908:Lens, Crystalline / Q000378:metabolism*; D008875:Middle Aged; D062105:Molecular Docking Simulation; D010084:Oxidation-Reduction / Q000187:drug effects; D011487:Protein Conformation; D014364:Tryptophan / Q000378:metabolism*; D038222:gamma-Crystallins / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D038222:gamma-Crystallins; D014364:Tryptophan; D002392:Catechin; D006861:Hydrogen Peroxide; C045651:epigallocatechin gallate
keywords: (−)-Epigallocatechin gallate; Human γ-crystallin; Oxidized Trp