Study of Tryptophan 2,3-dioxygenase self-association : a biochemical and biophysical analysis

Details

Supervisors

Frédérick, Raphaël

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences agronomiques, à finalité spécialisée

Abstract

Tryptophan 2,3-dioxygenase (TDO), which catalyzes the oxidative cleavage of L-tryptophan to N-formyl kynurenine in the kynurenine pathway, has been studied for many years as a potential target in cancer immunotherapy. This haemoprotein is overexpressed in the tumor microenvironment of more than half of solid tumors. TDO has two binding sites for its substrate: an exosite and an active site. The heme, essential for the enzymatic activity and quaternary structure of TDO, also binds to the active site. Inhibitors targeting the active site are already the subject of numerous studies. More recently, this enzyme has been investigated in the context of novel disruptive strategies. This study aimed to investigate the self-association of TDO using biophysical and biochemical methods. The study of both the apo and holo forms of TDO seems to reveal a link between the presence of a substrate, α-methyl tryptophan, in its exosite and the binding of heme. In contrast, the orthosteric inhibitor 37a, previously developed in the CMFA laboratory, did not establish a connection between its binding and heme binding. These findings open the door to the development of allosteric inhibitors of TDO. The production of mutated constructs of residues stabilizing the ligands in the active site demonstrated the importance of these residues for the enzymatic activity of TDO. They also suggest their involvement in stabilizing its quaternary structure.