Effect of 6-phosphogluconate on phosphoglucose isomerase in rat brain in vitro and in vivo

J Neurochem. 1989 May;52(5):1348-52. doi: 10.1111/j.1471-4159.1989.tb09178.x.

Abstract

The activity of phosphoglucose isomerase, its kinetic properties, and the effect of 6-phosphogluconate on its activity in the forward (glucose 6-phosphate----fructose 6-phosphate) and the reverse (fructose 6-phosphate----glucose 6-phosphate) reactions were determined in adult rat brain in vitro. The activity of phosphoglucose isomerase (in nmol/min/mg of whole brain protein) was 1,865 +/- 20 in the forward reaction and 1,756 +/- 32 in the reverse reaction at pH 7.5. It was 1,992 +/- 28 and 2,620 +/- 46, respectively, at pH 8.5. The apparent Km and Vmax of phosphoglucose isomerase were 0.593 +/- 0.031 mM and 2,291 +/- 61 nmol/min/mg of protein, respectively, for glucose 6-phosphate and 0.095 +/- 0.013 mM and 2,035 +/- 98 nmol/min/mg of protein, respectively, for fructose 6-phosphate. The activity of phosphoglucose isomerase was inhibited intensely and competitively by 6-phosphogluconate, with an apparent Ki of 0.048 +/- 0.005 mM for glucose 6-phosphate and 0.042 +/- 0.004 mM for fructose 6-phosphate as the substrate. With glucose 6-phosphate as the substrate, at concentrations from 0.05 to 0.5 mM, the activity of the enzyme was inhibited completely in the presence of 0.5-2.0 mM 6-phosphogluconate. With 0.05-0.2 mM fructose 6-phosphate as the substrate, it was inhibited greater than or equal to 85% at the same concentrations of the inhibitor. No significant changes were observed in the values of Km, Vmax, and Ki for phosphoglucose isomerase in the brain of 6-aminonicotinamide-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Comparative Study

MeSH terms

  • 6-Aminonicotinamide / pharmacology
  • Amino Acids / metabolism
  • Animals
  • Binding, Competitive
  • Brain / drug effects
  • Brain / enzymology*
  • Deoxyglucose / pharmacology
  • Fructosephosphates / metabolism
  • Gluconates / pharmacology*
  • Glucose / metabolism
  • Glucose-6-Phosphate
  • Glucose-6-Phosphate Isomerase / antagonists & inhibitors
  • Glucose-6-Phosphate Isomerase / metabolism*
  • Glucosephosphates / metabolism
  • Hydrogen-Ion Concentration
  • Kinetics
  • Male
  • Rats
  • Rats, Inbred Strains
  • Spectrophotometry

Substances

  • Amino Acids
  • Fructosephosphates
  • Gluconates
  • Glucosephosphates
  • 6-Aminonicotinamide
  • Glucose-6-Phosphate
  • fructose-6-phosphate
  • Deoxyglucose
  • Glucose-6-Phosphate Isomerase
  • Glucose
  • 6-phosphogluconic acid