Non-enzymatic glycosylation of proteins in biological sytem and its physiological significance in aging process.

蛋白质与葡萄糖的非酶糖基化反应称为美拉德反应，通过席夫碱加合物和Amadori重排产物，导致具有荧光、棕色和交联性质的高级糖基化终产物（AGE）。通过美拉德反应进行的体内蛋白质修饰。特别是年龄产物，被认为在痴呆并发症或衰老过程中起重要作用，尽管对AGE蛋白的化学结构一无所知。本课题主要研究AGE产物的生物学特性。还试图确定AGE产物的化学结构。主要研究结果如下：1. AGE-蛋白如AGE-白蛋白和AGE-血红蛋白经历受体介导的巨噬细胞或巨噬细胞衍生的细胞的内吞作用，包括大鼠肝窦细胞、大鼠和小鼠腹腔巨噬细胞和人单核细胞巨噬细胞。发现该受体与我们在1986年发现的一种针对β-环糊精修饰的蛋白质的清道夫受体相同。Cerami等声称2-（2-呋喃甲酰基）-4（5）-（呋喃基）-1H-咪唑（FFI）参与受体识别。然而，我们使用合成的FFI衍生物的实验清楚地表明，情况并非如此。通过使用抗FFI抗体的放射免疫测定和通过高效液相色谱法的测定证明，FFI实际上是AGE-蛋白质的酸水解和随后与氨反应后产生的伪像，这是FFI在体内存在的证据。主要的荧光化合物是从AGE-1-赖氨酸衍生物中分离出来的。免疫学分析表明，这种荧光化合物确实发生在年龄蛋白上。以上结果表明，AGE蛋白的一个共同结构可能是清道夫受体生物识别的关键。

Nonenzymatic glycosylation of proteins with glucose named the Maillard reaction leads, through a Schiff base adduct and Amadori rearrangement products, to advanced glycosylation end product (AGE) with fluorescence, brown color and cross-linked property. Protein modification in vivo by the Maillard reaction. Particularly age-products, is believed to play an important role in deabetic complications or aging processes, although nothing is known about a chemical structure(s) of AGE-proteins. In the present project, we elucidated the biological property of AGE-products. An attempt was also made to determine the chemical structure of AGE-product(s). Following results were obtained.1. AGE-proteins such as AGE-albumin and AGE-hemoglobin underwent receptor-mediated endocytosis by macrophages or macrophage-derived cells, including rat sinusoidal liver cells, rat and murine peritoneal macrophages and human monocyte macrophages. The receptor was found to be identical to a scavenger receptor for aldehyde-modified proteins which had been discovered by us in 1986.2. Cerami et al. claimed that 2-(2-furoyl)-4(5)-(furanyl)-1H-imidazole (FFI) was involved in the recepter recognition. However, our experiment using synthesized FFI derivatives clearly showed that this was not the case.3. Determination by the radioimmunoassay using an anti-FFI antibody and by high performance liquid chromatography demonstrated that FFI was in fact an artifact generated after acid hydrolysis of AGE-proteins and subsequent reaction with ammonia, evidence against in vivo presence of FFI.4. The major fluorescent compound was isolated from AGE-l-lysine derivatives. Immunological analyses indicated that this fluorescent compound did occur to age-proteins. Its precise chemical structure is being determined.The above results taken together suggest that a structure in common among AGE-proteins might be crucial to the biological recognition by the scavenger receptor.