Mechanism for activation of triosephosphate isomerase by phosphite dianion: the role of a hydrophobic clamp.

ABSTRACT: The role of the hydrophobic side chains of Ile-172 and Leu-232 in catalysis of the reversible isomerization of R-glyceraldehyde 3-phosphate (GAP) to dihydroxyacetone phosphate (DHAP) by triosephosphate isomerase (TIM) from Trypanosoma brucei brucei (Tbb) has been investigated. The I172A and L232A mutations result in 100- and 6-fold decreases in k(cat)/K(m) for the isomerization reaction, respectively. The effect of the mutations on the product distributions for the catalyzed reactions of GAP and of [1-(13)C]-glycolaldehyde ([1-(13)C]-GA) in D(2)O is reported. The 40% yield of DHAP from wild-type Tbb TIM-catalyzed isomerization of GAP with intramolecular transfer of hydrogen is found to decrease to 13% and to 4%, respectively, for the reactions catalyzed by the I172A and L232A mutants. Like

SUBMITTER: Malabanan MM 

PROVIDER: S-EPMC3380172 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature