LOW-BARRIER HYDROGEN-BONDS AND ENZYMATIC CATALYSIS
LOW-BARRIER HYDROGEN-BONDS AND ENZYMATIC CATALYSIS
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DOI：
10.1126/science.8009219
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发表时间：
1994-06-24
期刊：
影响因子：
56.9
通讯作者：
KREEVOY, MM
中科院分区：
文献类型：
--
作者：
CLELAND, WW;KREEVOY, MM
在过渡态或在酶-中间体复合体中形成一个短的(小于2.5埃)、非常强的、低势垒的氢键，可以对酶催化做出重要贡献。这种键的形成可以提供每摩尔10到20千卡的热量，从而促进困难的反应，如羧酸基的烯醇化。因为只有当共享氢的氧或氮的酸常数pK(A)‘S(酸常数的负对数)相似时，才会形成低势垒氢键，因此，如果pK(A)’S不匹配的酶-底物络合物中的pK(A)‘S在过渡态或酶-中间体络合物中匹配，则酶-底物络合物中的弱氢键可能变成强的低势垒氢键。
Formation of a short (less than 2.5 angstroms), very strong, low-barrier hydrogen bond in the transition state, or in an enzyme-intermediate complex, can be an important contribution to enzymic catalysis. Formation of such a bond can supply 10 to 20 kilocalories per mole and thus facilitate difficult reactions such as enolization of carboxylate groups. Because low-barrier hydrogen bonds form only when the pK(a)'s (negative logarithm of the acid constant) of the oxygens or nitrogens sharing the hydrogen are similar, a weak hydrogen bond in the enzyme-substrate complex in which the pK(a)'s do not match can become a strong, low-barrier one if the pK(a)'s become matched in the transition state or enzyme-intermediate complex. Several examples of enzymatic reactions that appear to use this principle are presented.