色氨酸通过犬尿氨酸通路被分解代谢,而遍布全身的吲哚胺2,3二加氧酶(IDO)则是犬尿氨酸通路的首要的限速酶.IDO通过把左旋色氨酸转化为甲酰犬尿氨酸,甲酰犬尿氨酸能快速地转化为更为稳定的犬尿氨酸分子.犬尿氨酸通路可有许多中间产物,大多都有活性调节的功能.现如今公认IDO为机体内重要的内源性免疫抑制剂,在维持机体免疫稳态,移植耐受、肿瘤局部免疫抑制微环境的形成和维持,以及在介导肿瘤的免疫逃逸中发挥重要作用.IDO的存在对自身免疫性疾病的防治研究有重要的影响,具有广阔的发展前景.%Tryptophan is catabolized by the kynurenine pathways of which the first and rate-limiting step is mediated by enzymes, indoleamine 2,3 dioxygenase(IDO )-active throughout the body. Lpon posttransla-tional activation IDO initiates kynurenine pathways through converting L-tryptophan to N-formylkynurenine, which is rapidly converted to the more stable kynurenine molecule. The kynurenine pathway comprises the generation of several intermediate products, most of which possess immunomodulatory activity. Nowadays it is universally acknowledged that IDO is an endogenous immunosuppressive enzyme which plays a significant role in keeping the balance of immune homeostasis, tumor transplantation tolerance, induction and mediation of partial tumor immune inhibition environment, and tumor immune escape. What's more, IDO is playing an important role in autoimmune diseases, where broad development prospects is expected.
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