Time-Resolved Enthalpy and Volume Changes for Co-Photorelease from Indoleamine 2,3-Dioxygenase

Abstract

Indoleamine 2,3-dioxygenase (IDO) is a heme protein catalyzing the first and rate limiting step in the metabolism of L-tryptophan via the kynurenine pathway. The enzyme is responsible for the insertion of dioxygen into the indole ring generating l-formyl-kynurenine. However, the mechanisms underlying ligand binding and the resulting protein conformational changes leading to the reaction products are not well understood. Photoacoustic calorimetry was utilized to probe conformational dynamics associated with CO photo-release from the ferrous form of IDO in the presence and absence of L-tryptophan.