EPR and Mossbauer spectroscopy show inequivalent hemes in tryptophan dioxygenase.

ABSTRACT: Tryptophan 2,3-dioxygenase (TDO) is an essential enzyme in the pathway of NAD biosynthesis and important for all living organisms. TDO catalyzes oxidative cleavage of the indole ring of L-tryptophan (L-Trp), converting it to N-formylkynurenine (NFK). The crystal structure of TDO shows a dimer of dimer quaternary structure of the homotetrameric protein. The four catalytic sites of the protein, one per subunit, contain a heme that catalyzes the activation and insertion of dioxygen into L-Trp. Because of the alpha(4) structure and because only one type of heme center has been identified in previous spectroscopic studies, the four hemes sites have been presumed to be equivalent. The present work demonstrates that the heme sites of TDO are not equivalent. Quantitative interpretation of EPR and

SUBMITTER: Gupta R 

PROVIDER: S-EPMC4251817 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature