Mycobacterium tuberculosis unusually excretes a large amount of this compound, which is the basis of a common test for identifying it that is named for this compound. The receptors HCA2 and HCA3 are alternatively named for this compound that binds to them. By binding to HCA2, this compound increases HDL levels but also causes flushing. This compound is directly synthesized from quinolinic acid, which is produced via the kynurenine pathway from (*) tryptophan. (10[1])Deficiency of this compound is characterized by the “three Ds” of diarrhea, dementia, and dermatitis, with dermatitis particularly affecting sunlight-exposed skin. Nixtamalization increases the bioavailability of this compound in maize. An amide of this compound is part of NAD and NADP. For 10 points, name this vitamin whose deficiency is pellagra. ■END■