AMINO-CARBONYL REACTIONS IN THE AGING HUMAN LENS

本提案的总体目标是确定生物化学基础 以及透镜老化中晶状体蛋白色素沉着和交联的机制 和白内障形成。 在过去两年半中取得的进展 本申请人的实验室揭示了透镜 色素沉着和戊糖苷，抗坏血酸衍生的蛋白质交联 在Maillard型反应中形成。 这一点和其他意见强烈 抗坏血酸氧化产物在透镜衰老中毒性 白内障形成 我们建议研究抗坏血酸盐转变为 美拉德反应物和抗坏血酸介导的程度 美拉德反应解释了人类透镜晶体蛋白色素沉着， 在老化和白内障形成中的交联。 具体来说，我们假设 在抗坏血酸调节之前， 透镜晶状体蛋白着色和通过美拉德反应交联。 为了澄清生化缺陷的性质， 将进行实验： 1.我们将首先确定抗坏血酸模式的差异， 年轻人、老年人和白内障患者晶状体中的降解产物， 阐明这些产物的结构。 2.我们将鉴定出含有抑制剂的特定人类透镜组分， 抗坏血酸介导的美拉德反应的活性， 表征抗坏血酸降解的生物化学性质 抑制活性。 3.我们将阐明高级美拉德产物的结构 具体抗坏血酸，特别是对长波结构的重点 荧光分子 4.最后，我们将系统地将特定缺陷与 抗坏血酸代谢在特定目标I-III中发现， 晶状体蛋白着色和交联以及特异性 高级美拉德反应产物作为年龄和存在的函数， 白内障 这个项目的成功完成可能会产生线索 一种新的白内障发生假说， 透镜中抗坏血酸代谢。

The overall objective of this proposal is to define the biochemical basis and mechanisms of crystallin pigmentation and crosslinking in lens aging and cataractogenesis. Progress achieved in the past 2 1/2 years in the applicant's laboratory unraveled a high correlation between lens pigmentation and pentosidine, an ascorbate-derived protein crosslink formed in a Maillard-type reaction. This and other observations strongly implicate toxicity of ascorbate oxidation products in lens senescence and cataractogenesis. We propose to investigate the mechanism(s) by which ascorbate turns into a Maillard reactant and the extent to which the ascorbate mediated Maillard reaction explains human lens crystallin pigmentation and crosslinking in aging and cataractogenesis. Specifically, we hypothesize that several lines of defense must be weakened before ascorbate mediates lens crystallin pigmentation and crosslinking by the Maillard reaction. In order to clarify the nature of the biochemical defect the following experiments will be performed: 1. We will first identify differences in patterns of ascorbate degradation products in young, old and cataractous human lenses and elucidate the structure of these products. 2. We will identify specific human lens fractions that contain inhibitory activity against the ascorbate mediated Maillard reaction and characterize the biochemical nature of the ascorbate degradation inhibitory activity(ies). 3. We will elucidate the structure of the advanced Maillard products specific for ascorbate, focusing especially on the structure of long-wave fluorescent molecules. 4. Finally, we will systematically correlate specific defects in ascorbate metabolism uncovered in specific aims I-III with extent of crystallin pigmentation and crosslinking and the presence of specific advanced Maillard reaction products as a function of age and presence of cataract. The successful completion of this project may result in generating clues for a novel hypothesis of cataractogenesis based on genetic defects in ascorbate metabolism in the lens.