Induction of Indoleamine 2,3-Dioxygenase in Tumor Cells Transplanted into Allogeneic Mouse: Interferon-γ is the Inducer
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The major catabolic pathway of tryptophan in mammals is the kynurenine pathway. In adult young man in fact about 90% of dietary tryptophan is metabolized along this pathway (Fig. 1) (Wolf, 1974). Although it has long been generally accepted that “hepatic” L-tryptophan 2,3-dioxygenase (tryptophan pyrrolase) is the sole enzyme that catalyzes the first step of this pathway, recent studies have revealed that another enzyme called indoleamine 2,3-dioxygenase (IDO), which catalyzes the same reaction as “hepatic” enzyme, does occur in various “extra-hepatic” organs of mammals [mouse (Yoshida et al., 1980; Yoshida et al., 1981), rat (Cook et al., 1980), rabbit (Hayaishi et al., 1975 and human (Yamazaki et al., 1985)].
KeywordsConditioned Medium Chlamydia Trachomatis Kynurenic Acid Kynurenine Pathway Tryptophan Depletion
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