Dickerson J E, Lou M F, Gracy R W
Cataract Research Group, Alcon Laboratories, Inc., Fort Worth, TX 76134, USA.
Curr Eye Res. 1995 Feb;14(2):163-6. doi: 10.3109/02713689508999929.
Glycation, the non-enzymatic addition of sugar or other carbonyl compounds to the amino groups of a protein, has been shown to occur with a variety of sugars and a diverse group of proteins. This type of alteration is believed to be an important component of aging for lens proteins and perhaps in cataractogenesis. Glycation has been shown to alter function and spectroscopic techniques have shown that in many cases conformational changes have occurred. Circular dichroism spectroscopy has documented modifications to alpha-crystallin tertiary structure induced by glucose and glucose 6-phosphate but generally no change to secondary structure. Ascorbate and is oxidized derivative dehydroascorbate have been shown to be powerful glycating agents as well as forming cross-links between peptide chains. In this study, alpha-crystallin incubated with ascorbic acid for one or two wk shows significant incorporation of ascorbate, non-reducible cross-links between the protein chains and altered CD spectra in the far UV region indicative of secondary structure modification.
糖基化是指糖或其他羰基化合物非酶促地添加到蛋白质的氨基上，已证明其可发生在多种糖类和不同种类的蛋白质之间。这种类型的改变被认为是晶状体蛋白老化以及可能在白内障形成过程中的一个重要组成部分。糖基化已被证明会改变功能，光谱技术表明在许多情况下会发生构象变化。圆二色光谱法已记录了由葡萄糖和6-磷酸葡萄糖诱导的α-晶状体蛋白三级结构的修饰，但二级结构一般没有变化。抗坏血酸及其氧化衍生物脱氢抗坏血酸已被证明是强大的糖基化剂，并且能在肽链之间形成交联。在本研究中，与抗坏血酸孵育一或两周的α-晶状体蛋白显示出抗坏血酸的显著掺入、蛋白质链之间不可还原的交联以及远紫外区域中表明二级结构修饰的CD光谱改变。
