Examination of the mechanism of sucrose synthetase by positional isotope exchange

Journal Article · Wed Feb 25 04:00:00 EST 1987 · J. Biol. Chem.; (United States)

OSTI ID:6596858

Singh, A N; Hester, L S; Raushel, F M

The mechanism of the sucrose synthetase reaction has been probed by the technique of positional isotope exchange. (beta-/sup 18/O/sub 2/, alpha beta-/sup 18/O)UDP-Glc has been synthesized starting from oxygen-18-labeled phosphate and the combined activities of carbamate kinase, hexokinase, phosphoglucomutase, and uridine diphosphoglucose pyrophosphorylase. The oxygen-18 at the alpha beta-bridge position of the labeled UDP-Glc has been shown to cause a 0.014 ppm upfield chemical shift in the 31P NMR spectrum of both the alpha- and beta-phosphorus atoms in UDP-Glc relative to the unlabeled compound. The chemical shift induced by each of the beta-nonbridge oxygen-18 atoms was 0.030 ppm. Incubation of (beta-/sup 18/O/sub 2/, alpha beta-/sup 18/O)UDP-Glc with sucrose synthetase in the presence and absence of 2,5-anhydromannitol did not result in any significant exchange of an oxygen-18 from the beta-nonbridge position to the anomeric oxygen of the glucose moiety. It can thus be concluded that either sucrose synthetase does not catalyze the cleavage of the scissile carbon-oxygen bond of UDP-Glc in the absence of fructose or, alternatively, the beta-phosphoryl group of the newly formed UDP is rotationally immobilized.

• Research Organization: Texas AandM Univ., College Station
• OSTI ID: 6596858
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 6; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMICAL SHIFT
DAYS LIVING RADIOISOTOPES
ENZYME ACTIVITY
ENZYMES
EVEN-EVEN NUCLEI
ISOTOPES
LIGASES
LIGHT NUCLEI
NMR SPECTRA
NUCLEI
ODD-ODD NUCLEI
OXYGEN 18
OXYGEN ISOTOPES
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PHOSPHORUS-GROUP TRANSFERASES
PHOSPHOTRANSFERASES
RADIOISOTOPES
SPECTRA
STABLE ISOTOPES
STRUCTURE-ACTIVITY RELATIONSHIPS
TRANSFERASES