Enzyme Architecture: Amino Acid Side-Chains That Function To Optimize the Basicity of the Active Site Glutamate of Triosephosphate Isomerase.

ABSTRACT: We report pH rate profiles for k_cat and K_m for the isomerization reaction of glyceraldehyde 3-phosphate catalyzed by wildtype triosephosphate isomerase (TIM) from three organisms and by ten mutants of TIM; and, for K_i for inhibition of this reaction by phosphoglycolate trianion (I^3-). The pH profiles for K_i show that the binding of I^3- to TIM (E) to form EH·I₃^- is accompanied by uptake of a proton by the carboxylate side-chain of E165, whose function is to abstract a proton from substrate. The complexes for several mutants exist mainly as E^-·I₃^- at high pH, in which cases the pH profiles define the p K_a for deprotonation of EH·I₃^-. The li

SUBMITTER: Zhai X 

PROVIDER: S-EPMC6037162 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature