Cofactor activity of dihydroflavin mononucleotide and tetrahydrobiopterin for murine epididymal indoleamine 2,3-dioxygenase.
Dihydroflavin mononucleotide (FMNH2) and tetrahydrobiopterin (BH4) serve as cofactors for indoleamine 2,3-dioxygenase isolated from mouse epididymis. The optimal pH was between 7 and 8, and FMNH2-dependent activity was 4 to 5-fold higher than activity with methylene blue as the electron donor. Using FMNH2 with a FMN reductase system, the enzyme exhibited higher efficiency and specificity for L-Trp (an apparent Km of 1 X 10(-5)M and an apparent Vmax of 182 nmol/min/mg of protein). The apparent Km and Vmax for D-Trp were 6.2 X 10(-5)M and 31 nmole/min/mg, respectively. Consequently, these observations appear to present the first evidence for a flavin-dependent mammalian dioxygenase.
D000818:Animals; D001708:Biopterins / Q000031:analogs & derivatives / Q000378:metabolism; D004822:Epididymis / Q000201:enzymology*; D005486:Flavin Mononucleotide / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D051379:Mice; D010105:Oxygenases / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism; D014366:Tryptophan Oxygenase
D001708:Biopterins; D005486:Flavin Mononucleotide; D014364:Tryptophan; D010105:Oxygenases; D014366:Tryptophan Oxygenase; C003402:sapropterin