Activation of tryptophan hydroxylase from slices of rat brain stem incubated with agents which promote calcium uptake or intraneuronal release.
Activation of tryptophan hydroxylase from slices of rat brain stem incubated with agents which promote calcium uptake or intraneuronal release.
复制标题
与促进钙吸收或神经元内释放的试剂一起孵育的大鼠脑干切片中色氨酸羟化酶的激活。
DOI：
10.1016/0006-2952(79)90194-1
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发表时间：
1979
影响因子：
5.8
通讯作者：
M. Boadle
中科院分区：
文献类型：
--
作者：
M. Boadle
已发现，在促进神经组织钙积累（无钠培养基，哇巴因。A23187）或神经元内从线粒体储存中释放钙（代谢抑制剂，氰化物，叠氮化物，鱼藤酮，胍和双香豆素）的条件下孵育大鼠脑干切片会导致色氨酸羟化酶活性的增加，色氨酸羟化酶的活性由低速上清液部分中的切片制剂制备，并在存在的情况下进行测定200 μML-色氨酸和 50 μMDL-6-甲基-5,6,7,8-四氢蝶呤 (6-MPH4)。用无 Na+ 培养基、乌巴因、离子载体 A23187、胍、氰化物或叠氮化物处理切片后酶活性的增加反映在酶的动力学特性改变上，即酶对底物和人工还原蝶呤辅因子的 Km 降低。此外，观察到 Vmax 略有增加，但并不总是具有统计显着性。对切片制剂进行不同处理后获得的动力学特性的改变与用在富钾培养介质中去极化的脑干切片制备的酶获得的相似。这种去极化诱导的色氨酸羟化酶激活是一种钙依赖性现象。与此一致的是，当从无Na + 培养基和含有哇巴因或A23187的培养基中省略钙离子时，没有观察到酶活性增加。去除外部钙并不能消除代谢抑制剂所获得的酶活性的增加，可能是因为这些物质从线粒体中释放钙。这些数据与以下观点一致：游离神经元内钙的增加会触发某些激活色氨酸羟化酶的生化事件。
Incubation of slices of rat brain stem under conditions that promote calcium accumulation by nerve tissue (Na-free medium, ouabain. A23187) or intraneuronal release of calcium from mitochondrial stores (metabolic inhibitors, cyanide, azide, rotenone, guanidine and dicoumarol) has been found to result in an increase in the activity of tryptophan hydroxylase, prepared from the slice preparations in a low speed supernatant fraction and assayed in the presence of 200 μML-tryptophan and 50 μMDL-6-methyl-5,6,7,8-tetrahydropterin (6-MPH4). The increase in enzyme activity following treatment of the slices with Na+-free medium, ouabain, ionophore A23187, guanidine, cyanide or azide was reflected in altered kinetic properties of the enzyme, namely a decrease in theKmof the enzyme for both substrate and artificial reduced pterin cofactor. In addition, a modest increase inVmaxwas observed, but was not always statistically significant. The alterations in kinetic properties obtained following the different treatments to the slice preparations were similar to those obtained with enzyme prepared from brain stem slices depolarized in a potassium-enriched incubation medium. This depolarization-induced activation of tryptophan hydroxylase is a calcium-dependent phenomenon. In agreement with this, no increase in enzyme activity was observed when calcium ions were omitted from the Na+-free medium and media containing ouabain or A23187. Removal of external calcium did not abolish the increase in enzyme activity obtained with metabolic inhibitors, presumably because these substances release calcium from mitochondria. The data are consistent with the view that a rise in free intraneuronal calcium triggers certain biochemical events which activate tryptophan hydroxylase.