Murine Epididymis Research Articles

Utilization of dihydroflavin mononucleotide and superoxide anion for the decyclization of l-tryptophan by murine epididymal indoleamine 2,3-dioxygenase

Dihydroflavin mononucleotide (FMNH 2) together with a regenerating enzyme system effectively supported l-tryptophan decyclization by indoleamine 2,3-dioxygenase isolated from murine epididymis. The native murine dioxygenase was a monomeric protein with M r 40,000 ± 1000, an apparent p I of 4.9 ± 0.1, and an optimum pH within the range of 7 to 8. Using FMNH 2 with FMN oxidoreductase, the enzyme attained significantly higher activity than the apparent maximal activity obtained by using the other electron donor systems examined (e.g., riboflavin, FAD, tetrahydrobiopterin, methylene blue). A kinetic study with the FMNH 2 cofactor suggested the occurrence of a complex reaction ( l-tryptophan-FMNH 2 interdependency) and a theoretical K′ m of 14 μ m or a K m of 13 μ m was estimated for the substrate. l-Tryptophan 2,3-dioxygenation was competitively inhibited by l-5-hydroxytryptophan with a K i of 1 μ m. The reaction rate was reduced to less than 50% of that of the control in the presence of Superoxide dismutase and was decreased to 3% of the control in the absence of catalase. Thus, Superoxide anion does not appear to be the only form of O 2 participating in the reaction. However, these data indicate that the activation of molecular oxygen is an essential factor for an optimum catalysis and a mechanism of FMNH 2-dependent oxygenation of l-tryptophan by murine indoleamine 2,3-dioxygenase.

Structural studies on the major antigenic determinant present in the murine epididymis and on the surface of functionally mature epididymal spermatozoa

Structural studies on the major antigenic determinant present in the murine epididymis and on the surface of functionally mature epididymal spermatozoa

Peptide synthesis by the murine epididymis

Peptide synthesis by the murine epididymis