Determination of the energetics of the UDP-glucose pyrophosphorylase reaction by positional isotope exchange inhibition

Journal Article · Tue Oct 06 04:00:00 EDT 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00394a026· OSTI ID:5512966

Hester, L S; Raushel, F M

A method has been developed for obtaining qualitative information about enzyme-catalyzed reactions by measuring the inhibitory effects of added substrates on positional isotope exchange rates. It has been demonstrated for ordered kinetic mechanisms that an increase in the concentration of the second substrate to add to the enzyme will result in a linear increase in the ratio of the chemical and positional isotope exchange rates. The slopes and intercepts from these plots can be used to determine the partitioning ratios of binary and ternary enzyme complexes. The method has been applied to the reaction catalyzed by UDP-glucose pyrophosphorylase. A positional isotope exchange reaction was measured within oxygen-18-labeled UTP as a function of variable glucose 1-phosphate concentration in the forward reaction. In the reverse reaction, a positional isotope exchange reaction was measured within oxygen-18-labeled UDP-glucose as a function of increasing pyrophosphate concentration. The results have been interpreted to indicate that the interconversion of the ternary central complexes is fast relative to product dissociation in either direction. In the forward direction, the release of UDP-glucose is slower than the release of pyrophosphate. The release of glucose 1-phosphate is slower than the release of UTP in the reverse reaction.

• Research Organization: Texas A and M Univ., College Station
• OSTI ID: 5512966
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:20; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
ALDEHYDES
AZINES
BIOCHEMICAL REACTION KINETICS
CARBOHYDRATES
CHROMATOGRAPHY
ENZYMES
EVEN-EVEN NUCLEI
GLUCOSE
HETEROCYCLIC COMPOUNDS
HEXOSES
HYDROXY COMPOUNDS
INHIBITION
ISOTOPES
ISOTOPIC EXCHANGE
KINETICS
LIGHT NUCLEI
LIQUID COLUMN CHROMATOGRAPHY
MONOSACCHARIDES
NMR SPECTRA
NUCLEI
NUCLEOSIDES
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN 18
OXYGEN ISOTOPES
PHOSPHORUS 31
PHOSPHORUS ISOTOPES
PHOSPHORUS-GROUP TRANSFERASES
PHOSPHOTRANSFERASES
PYRIMIDINES
REACTION KINETICS
RIBOSIDES
SACCHARIDES
SEPARATION PROCESSES
SPECTRA
STABLE ISOTOPES
SUBSTRATES
TRANSFERASES
URACILS
URIDINE