Bodaness R S, Leclair M, Zigler J S
Arch Biochem Biophys. 1984 Jun;231(2):461-9. doi: 10.1016/0003-9861(84)90409-0.
In contrast to other tissues, the lens exists in a milieu containing relatively high (micromolar) concentrations of H2O2. It has been demonstrated that activation of H2O2 to more-potent oxidant species via the heme-undecapeptide from cytochrome c produces alterations in lens crystallin polypeptides similar to the changes found in cataract. These include crystallin polypeptide crosslinking and the development of a blue fluorescence not attributable to tryptophan. Of the three classes of mammalian crystallins, gamma-crystallin is crosslinked by heme peptide-H2O2, whereas alpha and beta are not. Heme peptide plus H2O2 generates dityrosine from free tyrosine, and, concomitant with crosslinking, the gamma-crystallin exposed to this system develops a new fluorophor with the the characteristics of dityrosine. The findings with bovine and human crystallins are identical in this regard. In addition to the oxidation of tyrosine, exposure to heme peptide-H2O2 results in the oxidation of tryptophan. The intrinsic fluorescence of alpha, beta, and gamma-crystallins is due primarily to tryptophan, and the intrinsic fluorescence of each is decreased by heme peptide-H2O2. Thus, tryptophan oxidation occurs in all crystallins, but crosslinking occurs only in gamma-crystallin and is associated with oxidation of tyrosine.
与其他组织不同，晶状体所处的环境中过氧化氢（H2O2）浓度相对较高（微摩尔级）。业已证明，细胞色素c中的血红素十一肽可将H2O2激活为更强效的氧化物种，从而使晶状体晶状体蛋白多肽发生改变，类似于在白内障中发现的变化。这些变化包括晶状体蛋白多肽交联以及产生一种并非由色氨酸引起的蓝色荧光。在三类哺乳动物晶状体蛋白中，γ-晶状体蛋白可被血红素肽-H2O2交联，而α-晶状体蛋白和β-晶状体蛋白则不会。血红素肽加H2O2可从游离酪氨酸生成二酪氨酸，并且在交联的同时，暴露于该体系的γ-晶状体蛋白会形成一种具有二酪氨酸特征的新荧光团。在这方面，牛和人晶状体蛋白的研究结果是相同的。除了酪氨酸氧化外，暴露于血红素肽-H2O2还会导致色氨酸氧化。α-、β-和γ-晶状体蛋白的固有荧光主要归因于色氨酸，并且它们各自的固有荧光都会因血红素肽-H2O2而降低。因此，色氨酸氧化在所有晶状体蛋白中都会发生，但交联仅发生在γ-晶状体蛋白中，并且与酪氨酸氧化有关。
