Transition state structure of Salmonella typhimurium orotate phosphoribosyltransferase

Wen Tao, Charles Grubmeyer, John S. Blanchard

Research output: Contribution to journalArticle

67 Citations (Scopus)

Abstract

Orotate phosphoribosyltransferase (OPRTase) catalyzes the magnesium- dependent conversion of α-D-phosphoribosylpyrophosphate (PRPP) and orotate to orotidine 5'-monophosphate (OMP) and pyrophosphate. We have determined kinetic isotope effects on the reaction of OMP with pyrophosphate and with the pyrophosphate analog phosphonoacetic acid. In the latter case, full expression of the kinetic isotope effects allowed us to calculate the structure of the transition state for the pyrophosphorylytic reaction. The transition state resembles a classical oxocarbonium ion. Using the recently reported three-dimensional structures of the OPRTase-OMP (Scapin et al., 1994) and the OPRTase-PRPP complexes (Scapin et al., 1995a), we have modeled the calculated transition state structure into the active site of OPRTase. We propose a detailed chemical mechanism which is consistent with these results.

Original languageEnglish (US)
Pages (from-to)14-21
Number of pages8
JournalBiochemistry
Volume35
Issue number1
DOIs
StatePublished - Jan 9 1996

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Orotate Phosphoribosyltransferase
Salmonella
Salmonella typhimurium
Isotopes
Phosphonoacetic Acid
Kinetics
Magnesium
Catalytic Domain
Ions
diphosphoric acid
orotidylic acid

ASJC Scopus subject areas

  • Biochemistry

Cite this

Transition state structure of Salmonella typhimurium orotate phosphoribosyltransferase. / Tao, Wen; Grubmeyer, Charles; Blanchard, John S.

In: Biochemistry, Vol. 35, No. 1, 09.01.1996, p. 14-21.

Research output: Contribution to journalArticle

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N2 - Orotate phosphoribosyltransferase (OPRTase) catalyzes the magnesium- dependent conversion of α-D-phosphoribosylpyrophosphate (PRPP) and orotate to orotidine 5'-monophosphate (OMP) and pyrophosphate. We have determined kinetic isotope effects on the reaction of OMP with pyrophosphate and with the pyrophosphate analog phosphonoacetic acid. In the latter case, full expression of the kinetic isotope effects allowed us to calculate the structure of the transition state for the pyrophosphorylytic reaction. The transition state resembles a classical oxocarbonium ion. Using the recently reported three-dimensional structures of the OPRTase-OMP (Scapin et al., 1994) and the OPRTase-PRPP complexes (Scapin et al., 1995a), we have modeled the calculated transition state structure into the active site of OPRTase. We propose a detailed chemical mechanism which is consistent with these results.

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