The biological oxidation of L-tryptophan. (360G-Wellcome-083636_A_07_Z)

Oxidation of l-trptophan in all biological systems is catalysed by heme dioxygenases. The heme dioxygenases add a completely new dimension to the overall scope of reactivities known to be catalysed within the heme protein family. With heme proteins being used so ubiquitously across in biology, the dioxygenases therefore represent important targets. We have access to four different heme dioxygenases (bacterial and human tryptophan 2,3-dioxygenases (TDO) and indoleamine 2,3-dioxygenases (IDO)) . Recent breakthroughs, including new structures, provide us with a perfect opportunity to at last gain a detailed molecular insight. The objectives are: 1. To map the catalytic cycles of human and bacterial TDO/IDO. 2. To functionally characterise human TDO. 3. To use our unique structural framework to examine the factors affecting substrate binding across the family. 4. To examine the redox properties and to correlate this to functional work. 5. To determine new structures in cluding ternary complexes and mutant enzymes. 6. To generate a suite of site-directed variants to feed into our functional and structural analyses. The project builds on our preliminary published work and we have all the infrastructure and expertise needed to meet our goals. We expect the work to have major impact at the international level.