Shipanova I N, Glomb M A, Nagaraj R H
Center for Vision Research, Department of Ophthalmology, Case Western Reserve University and University Hospitals of Cleveland, Ohio 44106, USA.
Arch Biochem Biophys. 1997 Aug 1;344(1):29-36. doi: 10.1006/abbi.1997.0195.
The nonenzymatic Maillard reaction of proteins, initiated by the addition of sugars and other aldehydes and ketones, is thought to be an important mechanism in aging and the pathogenesis of diabetic complications. The alpha-dicarbonyl compounds are considered to be key intermediates in this reaction. Methylglyoxal (MG) (pyruvaldehyde), a physiological alpha-dicarbonyl compound, has been shown to modify proteins both in vitro and in vivo. Here we describe a novel fluorescent pyrimidine, N-delta-(5-hydroxy-4,6-dimethylpyrimidine-2-yl)-L-ornithine (argpyrimidine), formed from the Maillard reaction of MG with N-alpha-t-BOC-arginine. We find that the fluorescence spectrum of argpyrimidine is similar to that of methylglyoxal-modified proteins, suggesting that it is a major product in such modified proteins. HPLC-quantification of argpyrimidine in proteins incubated with methylglyoxal revealed a time-dependent formation. We detected significant amounts of argpyrimidine in incubations of N-alpha-t-BOC-arginine with micromolar concentrations of MG, and we find that various sugars and ascorbic acid serve as precursors. Our studies indicate that argpyrimidine is synthesized through an intermediate 3-hydroxypentane-2,4-dione and provide a chemical basis for fluorescence in proteins modified by methylglyoxal. We suggest that enhanced intrinsic fluorescence in diabetic proteins may be due, in part, to methylglyoxal-mediated Maillard reactions.
蛋白质的非酶糖基化反应（美拉德反应）由糖及其他醛类和酮类引发，被认为是衰老及糖尿病并发症发病机制中的一个重要机制。α-二羰基化合物被视为该反应的关键中间体。甲基乙二醛（MG）（丙酮醛）作为一种生理性α-二羰基化合物，已证实在体外和体内均可修饰蛋白质。在此，我们描述了一种新型荧光嘧啶，N-δ-（5-羟基-4,6-二甲基嘧啶-2-基）-L-鸟氨酸（精氨嘧啶），它由MG与N-α-叔丁氧羰基-精氨酸发生美拉德反应形成。我们发现精氨嘧啶的荧光光谱与甲基乙二醛修饰的蛋白质相似，这表明它是此类修饰蛋白质中的主要产物。用甲基乙二醛孵育蛋白质后，通过高效液相色谱法对精氨嘧啶进行定量分析，结果显示其形成具有时间依赖性。我们在N-α-叔丁氧羰基-精氨酸与微摩尔浓度MG的孵育体系中检测到了大量精氨嘧啶，并且发现各种糖类和抗坏血酸可作为其前体物质。我们的研究表明，精氨嘧啶是通过中间体3-羟基戊烷-2,4-二酮合成的，这为甲基乙二醛修饰的蛋白质产生荧光提供了化学基础。我们认为，糖尿病患者体内蛋白质固有荧光增强可能部分归因于甲基乙二醛介导的美拉德反应。
