Njoroge F G, Fernandes A A, Monnier V M
Institute of Pathology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106.
J Biol Chem. 1988 Aug 5;263(22):10646-52.
2-(2-Furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI) is a fluorescent molecule which was originally discovered in chloroform extract of ammoniacal solution of acid-hydrolyzed glycated proteins and proposed to represent a protein cross-link. The absence of a lysyl residue side chain and other observations promoted a detailed study of its mechanism of formation. Glycated alpha-t-Butoxycarbonyllysine was incubated for 29 days and periodically assayed for FFI and FFI-like fluorescence. Whereas fluorescence increased over time, FFI recovery was unexpectedly highest on day 0 and lowest on day 29, suggesting that FFI was directly derived from Amadori products. FFI was also recovered from hydrolysates of glycated neopentylamine, furosine, and browned poly-L-lysine but was virtually undetectable in similar solutions basified with NaOH, triethylamine, or pyridine instead of ammonia. Gas chromatography-mass spectrometry analysis of FFI from similar hydrolysates basified in the presence of 15N-enriched NH4Cl revealed for all precursors a parent ion peak at 230 instead of 228 m/e units, suggesting that the two imidazole nitrogen atoms had been incorporated from free ammonia into FFI. Spontaneous FFI synthesis occurred when furosine was reacted with aqueous ammonia at room temperature. These results do not support the proposition that FFI is an advanced glycosylation end product or a protein cross-link. They suggest that FFI is formed from ammonia and furosine which are by-products of acid-hydrolyzed glycated proteins.
2-(2-呋喃甲酰基)-4(5)-(2-呋喃基)-1H-咪唑(FFI)是一种荧光分子，最初是在酸水解糖化蛋白氨溶液的氯仿提取物中发现的，被认为代表一种蛋白质交联物。由于缺乏赖氨酰残基侧链以及其他观察结果，促使人们对其形成机制进行详细研究。将糖化的α-叔丁氧羰基赖氨酸孵育29天，并定期检测FFI和类似FFI的荧光。虽然荧光随时间增加，但FFI的回收率在第0天意外最高，在第29天最低，这表明FFI直接来源于阿马多里产物。FFI也从糖化新戊胺、果糖胺和褐变的聚-L-赖氨酸的水解产物中回收，但在用氢氧化钠、三乙胺或吡啶而不是氨碱化的类似溶液中几乎检测不到。对在含有15N标记氯化铵的情况下碱化的类似水解产物中的FFI进行气相色谱-质谱分析，结果显示所有前体的母离子峰在230 m/e处，而不是228 m/e，这表明两个咪唑氮原子是从游离氨掺入FFI中的。当果糖胺在室温下与氨水反应时会发生FFI的自发合成。这些结果不支持FFI是晚期糖基化终产物或蛋白质交联物的观点。它们表明FFI是由酸水解糖化蛋白的副产物氨和果糖胺形成的。
