Carbon Isotope Effect Study on Orotidine 5‘-Monophosphate Decarboxylase: Support for an Anionic Intermediate
| العنوان: | Carbon Isotope Effect Study on Orotidine 5‘-Monophosphate Decarboxylase: Support for an Anionic Intermediate |
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| المؤلفون: | W. Wallace Cleland, Jeremy L. Van Vleet, Annette Sievers, Laurie A. Reinhardt, Brian G. Miller |
| المصدر: | Biochemistry. 47:798-803 |
| بيانات النشر: | American Chemical Society (ACS), 2007. |
| سنة النشر: | 2007 |
| مصطلحات موضوعية: | chemistry.chemical_classification, Carbon Isotopes, Binding Sites, Protein Conformation, Chemistry, Decarboxylation, Orotidine-5'-Phosphate Decarboxylase, Inorganic chemistry, Substrate (chemistry), Protonation, bacterial infections and mycoses, complex mixtures, Biochemistry, Medicinal chemistry, Kinetics, chemistry.chemical_compound, Ylide, Orotidine, Kinetic isotope effect, bacteria, Mutant Proteins, Inductive effect, Carbanion |
| الوصف: | Orotidine 5'-monophosphate decarboxylase has been heavily examined in recent years due to its enzymatic proficiency, which provides a catalytic enhancement to a reaction rate approximately 1017 times greater than that of the nonenzymatic reaction. Several mechanisms proposed to explain this catalytic enhancement have included covalent addition, ylide or carbene formation, and most recently concerted protonation. All of these mechanisms have circumvented the formation of a high-energy vinyl anionic intermediate. To investigate the presence of an anionic intermediate, 13C isotope effect studies have been performed using the alternate substrate 5-fluoro-OMP (OMP = orotidine 5'-monophosphate). Isotope effects obtained for the wild-type enzyme with OMP and 5-fluoro-OMP are 1.0255 and 1.0106, respectively, corresponding to a decrease of approximately 1.5% for 5-fluoro-OMP. With the K59A enzyme, the intrinisic isotope effects show a similar decrease of approximately 1.9% from 1.0543 with OMP to 1.0356 with 5-fluoro-OMP. This decrease results from the inductive effect of the fluorine, which stabilizes the carbanion intermediate by electron withdrawal and produces a reaction with an earlier transition state. The isotope effect for the decarboxylation of the slow substrate 2'-deoxy-OMP produced a intrinsic isotope effect of nearly 1.0461. |
| تدمد: | 1520-4995 0006-2960 |
| الوصول الحر: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::b261b5a9897a1e043d8b1ccd28efd110Test https://doi.org/10.1021/bi701664nTest |
| رقم الانضمام: | edsair.doi.dedup.....b261b5a9897a1e043d8b1ccd28efd110 |
| قاعدة البيانات: | OpenAIRE |
| تدمد: | 15204995 00062960 |
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