The Heme Environment of Recombinant Human Indoleamine 2,3-Dioxygenase STRUCTURAL PROPERTIES AND SUBSTRATE-LIGAND INTERACTIONS

摘要: Indoleamine 2,3-dioxygenase is a heme enzyme that catalyzes the oxidative degradation of L-Trp and other indoleamines. We have used resonance Raman spectroscopy to characterize environment purified recombinant human indoleamine (hIDO). In absence L-Trp, spectrum Fe(3+) form displayed six-coordinate, mixed high low spin character. Addition triggered transition predominantly with two Fe-OH(-) stretching modes identified at 546 496 cm(-1), suggesting H-bonding between NH group pyrrole ring heme-bound OH(-). The distal pocket hIDO was explored further by an exogenous ligand, CN(-); again, binding introduced strong and/or steric interactions CN(-). On hand, Fe(2+) revealed five-coordinate or without bound. proximal Fe-His mode, 236 did not shift upon addition, indicating bond strength affected substrate. frequency suggests has "peroxidase-like" bond. Using CO as structural probe for in converted IDO peroxidase-like enzyme. Binding also caused conformational changes vinyl groups, which were independent coordination state iron. Together these data indicate l-Trp dioxygen are likely crucial enzymatic activity hIDO.