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Connecting Active‐Site Loop Conformations and Catalysis in Triosephosphate Isomerase: Insights from a Rare Variation at Residue 96 in the Plasmodial Enzyme
Author(s) -
Pareek Vidhi,
Samanta Moumita,
Joshi Niranjan V,
Balaram Hemalatha,
Murthy Mathur R. N.,
Balaram Padmanabhan
Publication year - 2016
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.201500532
Subject(s) - triosephosphate isomerase , residue (chemistry) , active site , stereochemistry , isomerase , serine , chemistry , enzyme , enzyme catalysis , enzyme kinetics , biochemistry
Despite extensive research into triosephosphate isomerases (TIMs), there exists a gap in understanding of the remarkable conjunction between catalytic loop‐6 (residues 166–176) movement and the conformational flip of Glu165 (catalytic base) upon substrate binding that primes the active site for efficient catalysis. The overwhelming occurrence of serine at position 96 (98 % of the 6277 unique TIM sequences), spatially proximal to E165 and the loop‐6 residues, raises questions about its role in catalysis. Notably, Plasmodium falciparum TIM has an extremely rare residue—phenylalanine—at this position whereas, curiously, the mutant F96S was catalytically defective. We have obtained insights into the influence of residue 96 on the loop‐6 conformational flip and E165 positioning by combining kinetic and structural studies on the PfTIM F96 mutants F96Y, F96A, F96S/S73A, and F96S/L167V with sequence conservation analysis and comparative analysis of the available apo and holo structures of the enzyme from diverse organisms.