| Autor: |
Cleland WW; Institute for Enzyme Research, University of Wisconsin, Madison 53705., Kreevoy MM |
| Jazyk: |
angličtina |
| Zdroj: |
Science (New York, N.Y.) [Science] 1994 Jun 24; Vol. 264 (5167), pp. 1887-90. |
| DOI: |
10.1126/science.8009219 |
| Abstrakt: |
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 pKa'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 pKa's do not match can become a strong, low-barrier one if the pKa's become matched in the transition state or enzyme-intermediate complex. Several examples of enzymatic reactions that appear to use this principle are presented. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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