Westwood M E, McLellan A C, Thornalley P J
Department of Chemistry and Biological Chemistry, University of Essex, Colchester, United Kingdom.
J Biol Chem. 1994 Dec 23;269(51):32293-8.
Methylglyoxal binds and irreversibly modifies arginine and lysine residues in bovine serum albumin (BSA) under physiological conditions, producing a protein with an increased net negative charge at physiological pH. At 4 degrees C, methylglyoxal-modified BSA (MG-BSA) was bound by cell surface receptors on murine P388D1 macrophages. The apparent dissociation constant KD value was 435 +/- 2 nM, and there were 8.89 +/- 0.02 x 10(5) receptors/cell (n = 6), compare with an apparent KD value of 263 +/- 52 nM and 10.17 +/- 0.93 x 10(5) receptors/cell (n = 11) for advanced glycation end product-modified BSA (AGE-BSA). AGE-BSA competed with MG-BSA for binding to a common receptor; however, a component of AGE-BSA receptor binding could not be displaced by MG-BSA, and a component of MG-BSA receptor binding could not be displaced by AGE-BSA, suggesting that there are binding sites for both AGE-BSA and MG-BSA, competitive and noncompetitive, to MG-BSA and AGE-BSA on P388D1 cells at 4 degrees C. At 37 degrees C, receptor binding of AGE-BSA and MG-BSA was followed by endocytosis and lysosomal degradation of the modified protein. Methylglyoxal-modified proteins are ligands for the AGE receptor, and their formation and metabolism may be linked to the development of diabetic complications.
在生理条件下，甲基乙二醛会与牛血清白蛋白（BSA）中的精氨酸和赖氨酸残基结合并发生不可逆修饰，从而产生一种在生理pH值下净负电荷增加的蛋白质。在4℃时，甲基乙二醛修饰的BSA（MG-BSA）被小鼠P388D1巨噬细胞的细胞表面受体所结合。表观解离常数KD值为435±2 nM，每个细胞有8.89±0.02×10⁵个受体（n = 6），相比之下，晚期糖基化终产物修饰的BSA（AGE-BSA）的表观KD值为263±52 nM，每个细胞有10.17±0.93×10⁵个受体（n = 11）。AGE-BSA与MG-BSA竞争结合共同受体；然而，AGE-BSA受体结合的一部分不能被MG-BSA取代，MG-BSA受体结合的一部分也不能被AGE-BSA取代，这表明在4℃时，P388D1细胞上存在AGE-BSA和MG-BSA的结合位点，对MG-BSA和AGE-BSA既有竞争性结合位点，也有非竞争性结合位点。在37℃时，AGE-BSA和MG-BSA的受体结合之后是修饰蛋白的内吞作用和溶酶体降解。甲基乙二醛修饰的蛋白质是AGE受体的配体，它们的形成和代谢可能与糖尿病并发症的发生有关。
