Flamigni F, Guarnieri C, Caldarera C M
Biochim Biophys Acta. 1984 Nov 28;802(2):245-52. doi: 10.1016/0304-4165(84)90168-5.
A highly purified preparation of heart ornithine decarboxylase was obtained from isoproterenol-treated rats. The molecular and catalytic properties of the cardiac enzyme were investigated. The isoelectric point of the enzyme appeared to be 4.9, and the molecular weight was estimated to be 54000 by SDS-polyacrylamide gel electrophoresis. Under nondenaturing conditions, the molecular weight of the partially purified enzyme was 10000-110000 as determined by gel filtration, whereas a significantly lower (Mr approx. 70000) value was obtained for purified ornithine decarboxylase. Both Km for the substrate and Vmax were affected by the dithiothreitol concentration in the assay mixture. In particular, the Km for ornithine was found to be about 0.09 mM in the presence of 2.9 mM dithiothreitol and appeared to decrease at lower dithiothreitol concentrations. The Km for pyridoxal phosphate was about 0.09 microM; putrescine and lysine inhibited the enzyme competitively, with Ki values of 1.3 and 11.7 mM, respectively. The existence of two different forms of ornithine decarboxylase in cardiac tissue was indicated by DEAE-cellulose chromatography.
从异丙肾上腺素处理的大鼠中获得了高度纯化的心脏鸟氨酸脱羧酶制剂。对该心脏酶的分子和催化特性进行了研究。该酶的等电点似乎为4.9，通过SDS-聚丙烯酰胺凝胶电泳估计其分子量为54000。在非变性条件下，通过凝胶过滤测定部分纯化酶的分子量为10000 - 110000，而纯化的鸟氨酸脱羧酶的分子量则明显较低（约70000）。测定混合物中的二硫苏糖醇浓度会影响底物的Km值和Vmax。特别是，在存在2.9 mM二硫苏糖醇的情况下，鸟氨酸的Km值约为0.09 mM，并且在较低的二硫苏糖醇浓度下似乎会降低。磷酸吡哆醛的Km值约为0.09 μM；腐胺和赖氨酸竞争性抑制该酶，Ki值分别为1.3和11.7 mM。DEAE-纤维素色谱表明心脏组织中存在两种不同形式的鸟氨酸脱羧酶。
