Rescue of K12G Triosephosphate Isomerase by Ammonium Cations: The Reaction of an Enzyme in Pieces
- 7 September 2010
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 132 (38), 13525-13532
- https://doi.org/10.1021/ja106104h
Abstract
The K12G mutation at yeast triosephosphate isomerase (TIM) results in a 5.5 × 105-fold decrease in kcat/Km for isomerization of glyceraldehyde 3-phosphate, and the activity of this mutant can be successfully “rescued” by NH4+ and primary alkylammonium cations. The transition state for the K12G mutant TIM-catalyzed reaction is stabilized by 1.5 kcal/mol by interaction with NH4+. The larger 3.9 kcal/mol stabilization by CH3CH2CH2CH2NH3+ is due to hydrophobic interactions between the mutant enzyme and the butyl side chain of the cation activator. There is no significant transfer of a proton from alkylammonium cations to GAP at the transition state for the K12G mutant TIM-catalyzed reaction, because activation by a series of RNH3+ shows little or no dependence on the pKa of RNH3+. A comparison of kcat/Km = 6.6 × 106 M−1 s−1 for the wildtype TIM-catalyzed isomerization of GAP and the third-order rate constant of 150 M−2 s−1 for activation by NH4+ of the K12G mutant TIM-catalyzed isomerization shows that stabilization of the bound transition state by the effectively intramolecular interaction of the cationic side chain of Lys-12 at wildtype TIM is 6.3 kcal/mol greater than that for the corresponding intermolecular interaction of NH4+ at K12G mutant TIM.Keywords
This publication has 43 references indexed in Scilit:
- Role of Lys-12 in Catalysis by Triosephosphate Isomerase: A Two-Part Substrate ApproachBiochemistry, 2010
- Activation of R235A Mutant Orotidine 5′-Monophosphate Decarboxylase by the Guanidinium Cation: Effective Molarity of the Cationic Side Chain of Arg-235Biochemistry, 2010
- Hydron Transfer Catalyzed by Triosephosphate Isomerase. Products of the Direct and Phosphite-Activated Isomerization of [1-13C]-Glycolaldehyde in D2OBiochemistry, 2009
- A Substrate in Pieces: Allosteric Activation of Glycerol 3-Phosphate Dehydrogenase (NAD+) by Phosphite DianionBiochemistry, 2008
- Formation and Stability of a Vinyl Carbanion at the Active Site of Orotidine 5‘-Monophosphate Decarboxylase: pKa of the C-6 Proton of Enzyme-Bound UMPJournal of the American Chemical Society, 2008
- Product Deuterium Isotope Effect for Orotidine 5‘-Monophosphate Decarboxylase: Evidence for the Existence of a Short-Lived Carbanion IntermediateJournal of the American Chemical Society, 2007
- Computational Modeling of the Catalytic Reaction in Triosephosphate IsomeraseJournal of Molecular Biology, 2004
- Crystal Structure of Triosephosphate Isomerase Complexed with 2-Phosphoglycolate at 0.83-Å ResolutionPublished by Elsevier BV ,2003
- Crystal Structure of the K12M/G15A Triosephosphate Isomerase Double Mutant and Electrostatic Analysis of the Active SiteBiochemistry, 1994
- Broønsted analysis of aspartate aminotransferase via exogenous catalysis of reactions of an inactive mutantProtein Science, 1992