Lysine 183 is the general base in the 6-phosphogluconate dehydrogenase-catalyzed reaction.
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.
Zhang
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Department of Chemistry and Biochemistry, University of Oklahoma, Norman 73019, USA.
Chooback
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Cook
P F
PF
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D002384:Catalysis; D003903:Deuterium / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008239:Lysine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010734:Phosphogluconate Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012756:Sheep
D011994:Recombinant Proteins; D003903:Deuterium; D010734:Phosphogluconate Dehydrogenase; D008239:Lysine