Catalytic activity of maize leaf phosphoenolpyruvate carboxylase in relation to oligomerization.
Catalytic activity of maize leaf phosphoenolpyruvate carboxylase in relation to oligomerization.
复制标题
玉米叶磷酸烯醇丙酮酸羧化酶与寡聚化的催化活性。
DOI：
10.1104/pp.80.4.848
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发表时间：
1986
期刊：
影响因子：
7.4
通讯作者：
G. Edwards
中科院分区：
文献类型：
--
作者：
G. H. Walker;M. Ku;G. Edwards
用体积排阻高效液相色谱法研究了玉米叶片磷酸烯醇式丙酮酸羧化酶的低聚状态与酶活性的关系。当100%的酶处于其四聚体形式时，发现每毫克蛋白质每分钟35至38微摩尔的最大活性。研究了巯基修饰剂CuCl（2）和对氯汞苯甲酸盐对酶抑制和蛋白质复合物聚集状态的影响。该酶的聚集对温度和pH敏感，低温和高pH有利于解聚。四聚体形式的稳定性在很大程度上取决于组氨酰残基，这在一定程度上解释了酶活性对MgCl（2）浓度变化的双相反应。通过抑制剂焦碳酸二乙酯（0.125毫摩尔）修饰四聚体的组氨酰残基导致其解离为二聚体形式并丧失活性。随后用0.4摩尔羟胺处理导致重新结合成四聚体并恢复酶活性。
The relationship between the state of oligomerization and activity of purified maize leaf phosphoenolpyruvate carboxylase using size exclusion high performance liquid chromatography was examined. Maximum activities of 35 to 38 micromoles per minute per milligram protein were found when 100% of the enzyme was in its tetrameric form. The effects of the sulfhydryl group modifiers CuCl(2) and p-chloromercuribenzoate on enzyme inhibition and the state of aggregation of the protein complex were examined. Aggregation of the enzyme is temperature and pH sensitive with low temperature and high pH favoring depolymerization. Stability of the tetrameric form is largely dependent upon histidyl residues, and to some extent this explains the biphasic response of enzyme activity to changes in MgCl(2) concentrations. Modification of the tetramer's histidyl residues by the inhibitor diethylpyrocarbonate (0.125 millimolar) results in its dissociation to the dimeric form and loss of activity. Subsequent treatment with 0.4 molar hydroxylamine results in reassociation to the tetramer and restoration of enzymic activity.