Solvent deuterium isotope effects in the catalysis of oxygen-18 exchange by human carbonic anhydrase II.
Solvent deuterium isotope effects in the catalysis of oxygen-18 exchange by human carbonic anhydrase II.
复制标题
溶剂氘同位素在人碳酸酐酶 II 催化氧 18 交换中的作用。
DOI：
10.1021/bi00268a006
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发表时间：
1982
期刊：
影响因子：
2.9
通讯作者：
Silverman,DN
中科院分区：
文献类型：
--
作者：
Tu,CK;Silverman,DN
摘要：通过测定无缓冲液条件下人碳酸酐酶II催化低硫酸根在HC03“和H20之间的交换速率，测定了含水底物氧的酶的释放速率。在pH(D)为5.8-8.0的范围内，在H20中测得的这个速率与在D20中测得的速率的比值在4到9之间，在pH(D)为6.6时的值为8.0±0.7(未校正的pH计读数)。在pH(D)为6.6时，这种同位素效应的大小与溶剂水中的氢原子分数成指数关系。我们的结论是，一个内部-
C. K. Tu and D. N. Silverman* abstract: By measuring the rate of exchange at chemical equilibrium of lsO between HC03 “and H20 catalyzed by human carbonic anhydrase II in the absence of buffers, we have determined the rate of release from the enzyme of water bearing substrate oxygen. The ratio of this rate measured in H20 to the rate measured in D20, the solvent deuterium isotope effect, is between 4 and 9 in the range ofpH (D) from 5.8 to 8.0, with a value of 8.0±0.7 at pH (D) 6.6 (uncorrected pH meter reading). The magnitude of this isotope effect at pH (D) 6.6 has an exponential dependence on the atom fraction of deuteriumin solvent water. We conclude that an intra-