question: What is the activity of Indoleamine 2,3-dioxygenase 1.
answer: Indoleamine 2,3-dioxygenase 1 (IDO1), a known immunosuppressive enzyme that catalyzes the rate-limiting step in the oxidation of tryptophan (Trp) to kynurenine (Kyn), has received increasing attention as an attractive immunotherapeutic target for cancer therapy.