摘要
在５℃、２０℃、３０℃，鸡肝二氢叶酸还原酶的活力随盐酸孤浓度增加，先经历一个激活区，以后则为失活区。温度升高，使最大激活幅度变小，激活区变窄，所需盐酸孤浓度减小。硫酸铵在浓度低于０．２ｍｏｌ／Ｌ时，对天然酶有较小的激活作用，更高浓度的硫酸按使酶活力下降；胍激活酶的活力随硫酸铵浓度的增加，由天然酶的２１０％单调下降；对失活酶，增加硫酸铵的浓度，则使酶活力逐渐恢复；三种情形的终活力均为天然酶的４０％。相应条件下的荧光光谱和圆二色谱的结果表明，硫酸铵对天然酶与激活酶的构象影响不大，但可使失活酶的构象恢复到与天然酶相似的状态。
The activity of dihydrofolate reductase from chicken liver goes first through an activated region and then an inactivated as the conCentration of guanidine hydrochloride increases at 5,20 and 30℃. The falsing of temperature made the activation region narrow, the maximum amplitude reduce and the denaturant concentration needed lower. The addition of ammonium sulfate deduced the similar effect and flattend the curves of the activity change. Ammonium sulfate activated the native enzyme slightly at concentrations of less than 0.2mol/L, while at higher concentrations the activity was decreased to 40%(taking activity of native enzyme as control). Increasing the concentration of ammonium sulfate, the activity of the activated enzyme decreased from 210% to 40% and that of the inactivatal enzyme recovered gradual from 0 to 40%. The results of fluorescence and CD spectroscopy under the re levant condition showed that ammonium sulfate affects little the conformation of native and activated enzyme, but recovered that of inactivatal enzyme nearly as same as native. These provide another evidence that the limited flexibility of the active site of the enzymes is necessary for its biological activity.
出处
《生物物理学报》
CAS
CSCD
北大核心
1995年第2期155-160,共6页
Acta Biophysica Sinica
关键词
二氢叶酸还原酶
激活
失活
盐酸胍
硫酸铵
Dihydrofolate reductase Activation Inactivation Guanidine hydrochloride
