MCAT Chemical and Physical Foundations of Biological Systems 17 — Flashcards

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Indoleamine 2,3-dioxygenase (IDO) 1 catalyzes the first and rate-limiting step of L-tryptophan degradation in the tryptophan-kynurenine pathway. The direct product of IDO1 is N´-formylkynurenine, which breaks down non-enzymatically to L-kynurenine by losing its formyl group. His-tagged human IDO1 cDNA was expressed in Escherichia coli and purified using a nickel column. IDO1 activity was measured in the absence and presence of various potential inhibitors in buffer at pH 6.5. Galanal was found to inhibit IDO1 activity, and based on the Michaelis-Menten kinetics of IDO1, its inhibitory mode was further studied by measuring the initial rate of L-kynurenine production in the presence and absence of 30 µM galanal at various L-tryptophan concentrations (Figure 1).