Fructose 2,6-bisphosphate (Fru-2,6-P/sub 2/) binds at the active site of rabbit liver fructose-1,6-bisphosphate
Fru-2,6-P/sub 2/ and AMP are potent inhibitors of fructose-1,6-bisphosphatase (FBPase). AMP inhibits by binding to an allosteric site. While Fru-2,6-P/sub 2/ and fructose 1,6-bisphosphate (Fru-1,6-P/sub 2/) binding is mutually exclusive, a controversy exists as to whether Fru-2,6-P/sub 2/ inhibits by binding to the active site or a regulatory site. To address this question, the aromatic region of the /sup 1/H NMR spectrum of FBPase was examined in the absence and presence of Fru-1,6-P/sub 2/, Fru-2,6-P/sub 2/, and AMP. All of the spectral perturbations produced by Fru-1,6-P/sub 2/ binding were also seen with Fru-2,6-P/sub 2/: (1) the C2-H of His 1 (pKa=7.1) shifted downfield 0.03 ppm (pH 5.3); (2) the C2-H of His 2 shifted downfield 0.03 ppm (pH 5.3) and broadened; (3) several resonances in the phe/tyr region of the spectrum decreased in intensity. In addition, both fructose bisphosphates produced a change in the exchange rate of AMP from past/intermediate in the binary enzyme AMP complex to slow exchange in the ternary complex. AMP produced similar changes in the phe/tyr region of the spectrum. Unlike the fructose bisphosphates, AMP binding produced: (1) broadening of the C2-H of His 1; (2) no effect on His 2 and; (3) an enhancement of the intensity of a resonance at 7.25 ppm (pH 5.3). The results are consistent with an active site binding mode of inhibition for Fru-2,6-P/sub 2/. AMP binding to a regulatory site was apparent from the different results obtained with this ligand.
- Research Organization:
- Iowa State Univ., Ames
- OSTI ID:
- 6527338
- Report Number(s):
- CONF-8606151-; TRN: 87-020092
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:6; Conference: 76. annual meeting of the Federation of American Society for Experimental Biology, Washington, DC, USA, 8 Jun 1986
- Country of Publication:
- United States
- Language:
- English
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62 RADIOLOGY AND NUCLEAR MEDICINE
PHOSPHATASES
NMR SPECTRA
RECEPTORS
PHOSPHATES
BIOCHEMICAL REACTION KINETICS
AMP
CHEMICAL SHIFT
FRUCTOSE
INHIBITION
LIGANDS
LIVER
NUCLEAR MAGNETIC RESONANCE
RABBITS
ANIMALS
BODY
CARBOHYDRATES
DIGESTIVE SYSTEM
ENZYMES
ESTERASES
GLANDS
HEXOSES
HYDROLASES
KETONES
KINETICS
MAGNETIC RESONANCE
MAMMALS
MEMBRANE PROTEINS
MONOSACCHARIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANS
OXYGEN COMPOUNDS
PHOSPHORUS COMPOUNDS
PROTEINS
REACTION KINETICS
RESONANCE
SACCHARIDES
SPECTRA
VERTEBRATES
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