AMINO-CARBONYL REACTIONS IN THE AGING HUMAN LENS

这项提案的总体目标是定义生化基础 晶状体老化过程中晶状体蛋白色素沉着和交联化的机制 和白内障的发生。在过去两年半内取得的进展 申请人的实验室揭开了晶状体之间的高度相关性 色素沉着与抗坏血酸衍生蛋白交联物--戊糖苷 在美拉德类型的反应中形成。这一点和其他强烈的观察结果 抗坏血酸氧化产物在晶状体衰老和损伤中的潜在毒性 白内障的发生。 我们建议研究(S)抗坏血酸转化为 一种美拉德反应物和抗坏血酸介导的程度 美拉德反应解释人类晶状体晶体蛋白色素沉着和 交联剂在衰老和白内障发生中的作用具体来说，我们假设 在抗坏血酸调停之前，必须削弱几条防线 晶状体中晶体蛋白通过美拉德反应着色和交联化。 为了澄清生化缺陷的性质，以下是 将进行以下实验： 1.我们将首先确定抗坏血酸模式的差异 青年、老年人和白内障患者晶状体中的降解产物和 阐明这些产品的结构。 2.我们将确定含有抑制性物质的特定人类晶状体部分 抗抗坏血酸介导的美拉德反应活性和 描述抗坏血酸降解的生化性质 抑制活性。 3.我们将阐明先进的美拉德产品的结构 专门针对抗坏血酸，特别关注长波的结构 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，范围 晶体蛋白的着色性和交联性以及特异性的存在 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导致产生线索 一种基于遗传缺陷的白内障发生的新假说 抗坏血酸在晶状体中的代谢。

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.