Seely J E, Pegg A E
Biochem J. 1983 Dec 15;216(3):701-7. doi: 10.1042/bj2160701.
A radioimmunoassay for ornithine decarboxylase was used to study the regulation of this enzyme in rat liver. The antiserum used reacts with ornithine decarboxylase from mouse, human or rat cells. Rat liver ornithine decarboxylase enzyme activity and enzyme protein (as determined by radioimmunoassay) were measured in thioacetamide-treated rats at various times after administration of 1,3-diaminopropane. Enzyme activity declined rapidly after 1,3-diaminopropane treatment as did the amount of enzyme protein, although the disappearance of enzyme activity slightly preceded the loss of immunoreactive protein. The loss of enzyme protein after cycloheximide treatment also occurred rapidly, but was significantly slower than that seen with 1,3-diaminopropane. When 1,3-diaminopropane and cycloheximide were injected simultaneously, the rate of disappearance of enzyme activity and enzyme protein was the same as that seen with cycloheximide alone. These results show that the rapid loss in enzyme activity after 1,3-diaminopropane treatment is primarily due to a loss in enzyme protein and that protein synthesis is needed in order for 1,3-diaminopropane to exert its full effect. A macromolecular inhibitor of ornithine decarboxylase that has been termed antizyme is induced in response to 1,3-diaminopropane, but our results indicate that the loss of enzyme activity is not due to the accumulation of inactive ornithine decarboxylase-antizyme complexes. It is possible that the antizyme enhances the degradation of the enzyme protein. Control experiments demonstrated that the antiserum used would have detected any inactive antizyme-ornithine decarboxylase complexes present in liver since addition of antizyme to ornithine decarboxylase in vitro did not affect the amount of ornithine decarboxylase detected in our radioimmunoassay. Anti-(ornithine decarboxylase) antibodies may be useful in the purification of antizyme since the antizyme-ornithine decarboxylase complex can be immunoprecipitated, and antizyme released from the precipitate with 0.3 M-NaCl.
采用鸟氨酸脱羧酶放射免疫分析法研究大鼠肝脏中该酶的调控。所用抗血清可与小鼠、人或大鼠细胞中的鸟氨酸脱羧酶发生反应。在给予1,3 - 二氨基丙烷后的不同时间，测定硫代乙酰胺处理大鼠的肝脏鸟氨酸脱羧酶活性和酶蛋白（通过放射免疫分析法测定）。1,3 - 二氨基丙烷处理后，酶活性迅速下降，酶蛋白量也随之下降，尽管酶活性的消失略早于免疫反应性蛋白的丢失。环己酰亚胺处理后酶蛋白的丢失也很快，但明显慢于1,3 - 二氨基丙烷处理后的情况。当同时注射1,3 - 二氨基丙烷和环己酰亚胺时，酶活性和酶蛋白的消失速率与单独使用环己酰亚胺时相同。这些结果表明，1,3 - 二氨基丙烷处理后酶活性的快速丧失主要是由于酶蛋白的丢失，并且1,3 - 二氨基丙烷要发挥其全部作用需要蛋白质合成。一种被称为抗酶的鸟氨酸脱羧酶大分子抑制剂在1,3 - 二氨基丙烷作用下被诱导产生，但我们的结果表明酶活性的丧失并非由于无活性的鸟氨酸脱羧酶 - 抗酶复合物的积累。抗酶可能增强了酶蛋白的降解。对照实验表明，所用抗血清能够检测到肝脏中存在的任何无活性的抗酶 - 鸟氨酸脱羧酶复合物，因为在体外将抗酶添加到鸟氨酸脱羧酶中并不影响我们放射免疫分析中检测到的鸟氨酸脱羧酶量。抗（鸟氨酸脱羧酶）抗体可能有助于抗酶的纯化，因为抗酶 - 鸟氨酸脱羧酶复合物可被免疫沉淀，并且用0.3M - NaCl可从沉淀物中释放出抗酶。
