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  • Title: Lysine 183 is the general base in the 6-phosphogluconate dehydrogenase-catalyzed reaction.
    Author: Zhang L, Chooback L, Cook PF.
    Journal: Biochemistry; 1999 Aug 31; 38(35):11231-8. PubMed ID: 10471272.
    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.
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