Gibbons R A, Dixon S N, Hallis K, Russell A M, Sansom B F, Symonds H W
Biochim Biophys Acta. 1976 Aug 24;444(1):1-10. doi: 10.1016/0304-4165(76)90218-x.
When 54MnCl2 was incubated with fresh bovine or caprine serum for 20 h and the serum subjected to electrophoresis at pH 9.5, the 54Mn bound to transferrin and alpha2-macroglobulin in proportions which varied with the temperature of incubation and the temperature of electrophoresis. Between 0 and 37 degrees C, the higher the temperature of incubation the larger the proportion bound to transferrin and the lower the proportion bound to alpha2-macroglobulin. The temperature at which electrophoresis was performed had little effect on the proportion of 54Mn bound to transferrin, but increasing temperature reduced the proportion of 54Mn bound to alpha2-macroglobulin. Mn2+ did not bind to purified transferrin in vitro in the absence of an oxidising agent. In the presence of permanganate, Mn3+ was formed and chelated by transferrin at physiological pH. In fresh serum this oxidation step may be performed by ceruloplasmin or molecular oxygen. Mn2+ was bound reversibly to alpha2-macroglobulin but this protein played no part in the oxidation of divalent manganese and had no effect on the protein binding of trivalent manganese. Manganese in the divalent state, either free as Mn2+ or bound to alpha2-macroglobulin, is removed from blood plasma very efficiently by the liver. However, the manganic-transferrin complex normally found in circulation is not rapidly removed from plasma. The liver can remove large amounts of excess manganous manganese which it presumably excretes; the small essential fraction of the manganese absorbed is oxidised to the trivalent state and bound to transferrin.
当将54MnCl2与新鲜的牛血清或羊血清一起孵育20小时，然后将血清在pH 9.5条件下进行电泳时，54Mn与转铁蛋白和α2-巨球蛋白结合的比例会随孵育温度和电泳温度而变化。在0至37摄氏度之间，孵育温度越高，与转铁蛋白结合的比例越大，与α2-巨球蛋白结合的比例越低。进行电泳的温度对54Mn与转铁蛋白结合的比例影响很小，但升高温度会降低54Mn与α2-巨球蛋白结合的比例。在没有氧化剂的情况下，Mn2+在体外不会与纯化的转铁蛋白结合。在高锰酸盐存在下，会形成Mn3+并在生理pH条件下被转铁蛋白螯合。在新鲜血清中，这个氧化步骤可能由铜蓝蛋白或分子氧完成。Mn2+可逆地与α2-巨球蛋白结合，但这种蛋白质在二价锰的氧化过程中不起作用，对三价锰的蛋白质结合也没有影响。二价状态的锰，无论是以Mn2+形式游离存在还是与α2-巨球蛋白结合，都能被肝脏非常有效地从血浆中清除。然而，通常在循环中发现的锰-转铁蛋白复合物不会很快从血浆中清除。肝脏可以清除大量多余的二价锰，推测这些二价锰会被排泄掉；吸收的少量必需锰会被氧化成三价状态并与转铁蛋白结合。
