Ranney H M, Lam R, Rosenberg G
Department of Medicine, Veterans Affairs Medical Center, University of California, San Diego.
Am J Hematol. 1993 Jan;42(1):107-11. doi: 10.1002/ajh.2830420121.
While no significant physiologic function of hemoglobin A2 (Hb A2), the minor basic component of human hemoglobin, has been recognized, only its oxygen equilibria have been studied in detail. Since hemoglobin A2 and its oxidative denaturation product, hemichrome A2, bind to the red cell membrane, particularly to band 3, to a greater extent than do Hb A or hemichrome A, some of the properties of Hb A2 that might influence hemoglobin-membrane association were examined. Hemoglobin A2 exhibited slightly increased susceptibility to autoxidation to methemoglobin. No differences were noted between methemoglobins A and A2, including the rates of enzymatic reduction and stability of the heme-globin linkage. Oxyhemoglobin A2 had a slightly lower solubility in phosphate buffer than did hemoglobin A. While the hemichromes (prepared with phenylhydrazine) of hemoglobins A2 and A had the same optical spectra, the A2 hemichrome exhibited greater stability. It is suggested that the differences in products of oxidative denaturation may provide the basis for functional differences between hemoglobins A2 and A.
虽然人类血红蛋白的次要碱性成分血红蛋白A2（Hb A2）尚未被确认有显著的生理功能，但仅对其氧平衡进行了详细研究。由于血红蛋白A2及其氧化变性产物高铁血红素A2比Hb A或高铁血红素A与红细胞膜，特别是与带3的结合程度更高，因此研究了Hb A2可能影响血红蛋白与膜结合的一些特性。血红蛋白A2对自动氧化为高铁血红蛋白的敏感性略有增加。高铁血红蛋白A和A2之间未发现差异，包括酶促还原速率和血红素-珠蛋白连接的稳定性。氧合血红蛋白A2在磷酸盐缓冲液中的溶解度略低于血红蛋白A。虽然血红蛋白A2和A的高铁血红素（用苯肼制备）具有相同的光谱，但A2高铁血红素表现出更高的稳定性。有人提出，氧化变性产物的差异可能为血红蛋白A2和A之间的功能差异提供基础。
