Reaction of 5-enol-pyruvoylshikimate-3-phosphate synthase with diethyl pyrocarbonate: evidence for an essential histidine residue
| Autor: | Quang Khai Huynh |
|---|---|
| Rok vydání: | 1987 |
| Předmět: |
Chemical Phenomena
Formates Stereochemistry Biophysics Hydroxylamine Hydroxylamines Biochemistry Catalysis chemistry.chemical_compound Structure-Activity Relationship Reaction rate constant Transferases Diethyl Pyrocarbonate Escherichia coli Histidine Molecular Biology chemistry.chemical_classification Alkyl and Aryl Transferases Binding Sites biology ATP synthase Active site Hydrogen-Ion Concentration Phosphate Chemistry Kinetics Enzyme chemistry Spectrophotometry biology.protein 3-Phosphoshikimate 1-Carboxyvinyltransferase Phosphoenolpyruvate carboxykinase |
| Zdroj: | Archives of biochemistry and biophysics. 258(1) |
| ISSN: | 0003-9861 |
| Popis: | 5-enol-Pyruvoylshikimate-3-phosphate synthase catalyzes the reversible condensation of phosphoenolpyruvate and shikimate 3-phosphate to yield 5-enol-pyruvoylshikimate 3-phosphate and inorganic phosphate. The enzyme is a target for the nonselective herbicide glyphosate (N-phosphonomethylglycine). Diethyl pyrocarbonate inactivated this enzyme with a second-order rate constant of 220 m −1 min−1 at pH 7.0 and 0 °C. The rate of inactivation is pH dependent and the pH inactivation rate data show the involvement of a group with a pKa of 6.8. Almost all of the original activity was recovered by treatment of the inactivated enzyme with hydroxylamine. The difference spectrum of the inactivated and native enzyme reveals a single peak at 242 nm but no trough at around 278 nm is observed. Complete inactivation required the modification of four histidine residues per molecule of the enzyme. However, statistical analysis of the residual activity and the extent of modification shows that among the four modifiable residues, only one is critical for activity. Furthermore, this inactivation is prevented by the substrates of the enzyme. The above results indicated that one histidine is located within or very close to the active site and may play an important role in catalysis. |
| Databáze: | OpenAIRE |
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