Mansouri A
Hematology Division, University of Arkansas for Medical Sciences, Little Rock.
Biochem Med Metab Biol. 1989 Aug;42(1):43-51. doi: 10.1016/0885-4505(89)90039-x.
Pure methemoglobin was prepared from fresh red cells and was used as substrate for methemoglobin reduction reaction. Two sources of methemoglobin reductase were used: (a) red cell hemolysate which was prepared by freezing and thawing of unwashed red cells; (b) purified methemoglobin reductase from bank blood. Methemoglobin reduction rate was measured in a mixture of pure methemoglobin (substrate) and hemolysate (enzyme). In other experiments the rate of methemoglobin reduction was measured in the above mixture with the addition of various other compounds such as NADH, cytochrome b5, and pure methemoglobin reductase. Only the addition of pure enzyme accelerated the rate of methemoglobin reduction. In other experiments, the rate of methemoglobin reduction was measured when the reduction reaction was carried out in the presence of various amounts of deoxyhemoglobin, globin, or albumin. It was shown that all proteins tested here decreased the reduction rate. It is concluded that (a) in the red cell, under normal conditions, only the activity of the methemoglobin reductase controls the speed of methemoglobin reduction, and (b) the inhibition of methemoglobin reduction by reduced hemoglobin is mostly nonspecific suggesting a noncompetitive reaction.
纯高铁血红蛋白由新鲜红细胞制备而成，并用作高铁血红蛋白还原反应的底物。使用了两种高铁血红蛋白还原酶来源：(a) 通过未洗涤红细胞的冻融制备的红细胞溶血产物；(b) 从库存血中纯化的高铁血红蛋白还原酶。在纯高铁血红蛋白（底物）和溶血产物（酶）的混合物中测量高铁血红蛋白还原率。在其他实验中，在上述混合物中添加各种其他化合物（如NADH、细胞色素b5和纯高铁血红蛋白还原酶）后测量高铁血红蛋白还原率。只有添加纯酶能加快高铁血红蛋白的还原速度。在其他实验中，当还原反应在各种量的脱氧血红蛋白、珠蛋白或白蛋白存在下进行时，测量高铁血红蛋白还原率。结果表明，此处测试的所有蛋白质均降低了还原率。得出的结论是：(a) 在红细胞中，在正常情况下，只有高铁血红蛋白还原酶的活性控制高铁血红蛋白还原的速度；(b) 还原血红蛋白对高铁血红蛋白还原的抑制大多是非特异性的，提示为非竞争性反应。
