Dr. Nina Goodey
Montclair State University
Department of Chemistry and Biochemistry
September 27, 2024
12:00 Noon
Room 120 – Meyerhoff Chemistry Building
Host: Dr. Songon An
“Roles of Active Site Residues in Mycobacterium tuberculosis Indole-3-glycerol Phosphate Synthase, a Potential Target for Antitubercular Agents”
Mycobacterium tuberculosis indole-3-glycerol phosphate synthase (MtIGPS) catalyzes the fourth step in the tryptophan biosynthesis pathway. This enzyme is vital for the bacterium’s replication and virulence, making it a promising target for new anti-tuberculosis drugs. We examined the roles of key active site residues through site-directed mutagenesis, revealing that mutations at these positions lead to significant reductions or complete loss of enzymatic activity, highlighting their essential roles in catalysis and substrate binding. Kinetic studies and rate-pH profiles identified coordinated interactions between Glu57, Lys119, and Glu219, which modulate the orientation and protonation state of catalytic acid Lys119, thereby influencing overall enzyme function.
The Glu57Asp mutant exhibited an unusual inverse solvent viscosity effect (SVE), coupled with a 50-fold decrease in catalytic efficiency, indicating a disruption in the active site’s function. Temperature studies indicated that the activity of the shorter Asp sidechain containing Glu57Asp mutant was more sensitive to changes is temperature. This suggests that the unusual inverse SVE may stem from a more flexible Lys119, unable to optimally perform catalysis. Computational docking and molecular dynamics simulations further elucidated the enzyme’s mechanism and provided insights into the interactions of substrate analogs and intermediates within the active site during different stages of the catalytic mechanism.