Engerson T D, McKelvey T G, Rhyne D B, Boggio E B, Snyder S J, Jones H P
J Clin Invest. 1987 Jun;79(6):1564-70. doi: 10.1172/JCI112990.
In response to global ischemia, tissue xanthine dehydrogenase was converted to xanthine oxidase in all tissues with half-times of conversion at 37 degrees C of approximately 3.6, 6, 7, and 14 h for the liver, kidney, heart, and lung, respectively. The time course of enzyme conversion at 4 degrees C was greatly extended with half-conversion times of 6, 5, 5, and 6 d for the respective tissues. Increases in xanthine oxidase activity were accompanied by the appearance of a distinct new protein species with greater electrophoretic mobility. The oxidase from ischemic rat liver was purified 781-fold and found to migrate with a higher mobility on native gels than the purified native dehydrogenase. Sodium dodecyl sulfate profiles revealed the presence of a single major band of 137 kD for the native dehydrogenase, whereas the oxidase had been partially cleaved generating polypeptides of 127, 91, and 57 kD. Polypeptide patterns for the oxidase resemble those seen following limited in vitro proteolysis of the native dehydrogenase supporting a proteolytic mechanism for the conversion of xanthine dehydrogenase to oxidase in ischemic rat liver.
在全局缺血的情况下，组织中的黄嘌呤脱氢酶在所有组织中均转化为黄嘌呤氧化酶，在37℃时，肝脏、肾脏、心脏和肺的转化半衰期分别约为3.6、6、7和14小时。在4℃时，酶转化的时间进程大大延长，各组织的半转化时间分别为6、5、5和6天。黄嘌呤氧化酶活性的增加伴随着一种电泳迁移率更高的独特新蛋白质的出现。来自缺血大鼠肝脏的氧化酶被纯化了781倍，并且发现在天然凝胶上的迁移率比纯化的天然脱氢酶更高。十二烷基硫酸钠图谱显示，天然脱氢酶存在一条137 kD的主要条带，而氧化酶已被部分切割，产生了127、91和57 kD的多肽。氧化酶的多肽模式类似于天然脱氢酶在有限的体外蛋白水解后所观察到的模式，这支持了缺血大鼠肝脏中黄嘌呤脱氢酶向氧化酶转化的蛋白水解机制。
