The presence of indolylamine 2,3-dioxygenase was examined in human subjects by determining its activity with L-tryptophan as substrate. Enzyme activity was detected in various tissues, and was relatively high in the lung, small intestine and placenta. Human indolylamine 2,3-dioxygenase, partially purified from the placenta, had an Mr of about 40 000 by gel filtration and exhibited a single pI of 6.9. The human enzyme required a reducing system, ascorbic acid and Methylene Blue, for maximal activity and was able to oxidize D-tryptophan, 5-hydroxy-L-tryptophan as well as L-tryptophan, but kinetic studies indicated that the best substrate of the enzyme was L-tryptophan.
Human indolylamine 2,3-dioxygenase. Its tissue distribution, and characterization of the placental enzyme
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F Yamazaki, T Kuroiwa, O Takikawa, R Kido; Human indolylamine 2,3-dioxygenase. Its tissue distribution, and characterization of the placental enzyme. Biochem J 15 September 1985; 230 (3): 635–638. doi: https://doi.org/10.1042/bj2300635
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