Observation by sup 13 C NMR of the EPSP synthase tetrahedral intermediate bound to the enzyme active site
- Monsanto Agricultural Company, St. Louis, MO (USA)
- Pennsylvania State Univ., University Park (USA)
Direct observation of the tetrahedral intermediate in the EPSP synthase reaction pathway was provided by {sup 13}C NMR by examining the species bound to the enzyme active site under internal equilibrium conditions and using (2-{sup 13}C)PEP as a spectroscopic probe. The tetrahedral center of the intermediate bound to the enzyme gave a unique signal appearing at 104 ppm. Separate signals were observed for free EPSP and EPSP bound to the enzyme in a ternary complex with phosphate. These peak assignments account for the quantitation of the species bound to the enzyme and liberated upon quenching with either triethylamine or base. A comparison of quenching with acid, base, or triethylamine was conducted. After long times of incubation during the NMR measurement, a signal at 107 ppm appeared. The compound giving rise to this resonance was isolated and identified as an EPSP ketal. The rate of formation of the EPSP ketal was very slow establishing that it is a side product of the normal enzymatic reaction. To look for additional signals that might arise from a covalent adduct which has been postulated to arise from reaction of enzyme with PEP, and NMR experiment was performed with an analogue of S3P lacking the 4- and 5-hydroxyl groups. All of these results reaffirm identification of the tetrahedral species as the only observable intermediate in the EPSP synthase reaction.
- OSTI ID:
- 7100660
- Journal Information:
- Biochemistry; (USA), Vol. 29:6; ISSN 0006-2960
- Country of Publication:
- United States
- Language:
- English
Similar Records
Phosphorus-31, sup 15 N, and sup 13 C NMR of glyphosate: Comparison of pH titrations to the herbicidal dead-end complex with 5-enolpyruvoylshikimate-3-phosphate synthase
/sup 13/C NMR studies of porphobilinogen synthase: observation of intermediates bound to a 280,000-dalton protein
Related Subjects
LIGASES
NUCLEAR MAGNETIC RESONANCE
SHIKIMIC ACID
BIOLOGICAL PATHWAYS
CARBON 13
LIQUID COLUMN CHROMATOGRAPHY
NMR SPECTRA
PHOSPHOENOLPYRUVATE
CARBON ISOTOPES
CARBOXYLIC ACIDS
CHROMATOGRAPHY
ENZYMES
EVEN-ODD NUCLEI
HYDROXY ACIDS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
RESONANCE
SEPARATION PROCESSES
SPECTRA
STABLE ISOTOPES
550601* - Medicine- Unsealed Radionuclides in Diagnostics