Lysine 183 Is the General Base in the 6-phosphogluconate Dehydrogenase-Catalyzed Reaction

Biochemistry. 1999 Aug 31;38(35):11231-8. doi: 10.1021/bi990433i.

Abstract

Site-directed mutagenesis was used to change K183 of sheep liver 6-phosphogluconate dehydrogenase to A, E, H, C, Q, R, and M to probe its possible role as a general base catalyst. Each of the mutant proteins was characterized with respect to its kinetic parameters at pH 7 and the pH dependence of kinetic parameters for the K183R mutant enzyme. The only mutant enzyme that gives a significant amount of catalysis is the K183R mutant, and the extent of catalysis is decreased by about 3 orders of magnitude; the general base pK is perturbed to a pH value of >9. All other mutant enzymes exhibit rates that are decreased by about 4 orders of magnitude compared to that of the wild-type enzyme. Data are consistent with the general base function of K183.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution / genetics
  • Animals
  • Catalysis
  • Deuterium / chemistry
  • Hydrogen-Ion Concentration
  • Kinetics
  • Liver / enzymology
  • Lysine / chemistry
  • Lysine / genetics
  • Lysine / metabolism*
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Phosphogluconate Dehydrogenase / chemistry
  • Phosphogluconate Dehydrogenase / genetics
  • Phosphogluconate Dehydrogenase / metabolism*
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Sheep

Substances

  • Recombinant Proteins
  • Deuterium
  • Phosphogluconate Dehydrogenase
  • Lysine