title: Direct spectroscopic detection of a C-H-cleaving high-spin Fe(IV) complex in a prolyl-4-hydroxylase.
abstract: The Fe(II)- and alpha-ketoglutarate (alphaKG)-dependent dioxygenases use mononuclear nonheme iron centers to effect hydroxylation of their substrates and decarboxylation of their cosubstrate, alphaKG, to CO(2) and succinate. Our recent dissection of the mechanism of taurine:alphaKG dioxygenase (TauD), a member of this enzyme family, revealed that two transient complexes accumulate during catalysis in the presence of saturating substrates. The first complex contains the long-postulated C-H-cleaving Fe(IV)-oxo intermediate, J, and the second is an enzyme.product(s) complex. Here, we demonstrate the accumulation of two transient complexes in the reaction of a prolyl-4-hydroxylase (P4H), a functional homologue of human alphaKG-dependent dioxygenases with essential roles in collagen biosynthesis and oxygen sensing. The kinetic and spectroscopic properties of these two P4H complexes suggest that they are homologues of the TauD intermediates. Most notably, the first exhibits optical absorption and Mössbauer spectra similar to those of J and, like J, a large substrate deuterium kinetic isotope on its decay. The close correspondence of the accumulating states in the P4H and TauD reactions supports the hypothesis of a conserved mechanism for substrate hydroxylation by enzymes in this family.
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Lee M
authors.initials: LM
authors.lastname: Hoffart
authors.forename: Eric W
authors.initials: EW
authors.lastname: Barr
authors.forename: Robert B
authors.initials: RB
authors.lastname: Guyer
authors.forename: J Martin
authors.initials: JM
authors.lastname: Bollinger
authors.forename: Carsten
authors.initials: C
authors.lastname: Krebs
mesh_terms: D000042:Absorption; D000595:Amino Acid Sequence; D002244:Carbon / Q000032:analysis*; D006801:Humans; D006859:Hydrogen / Q000032:analysis*; D007501:Iron / Q000032:analysis*; D007656:Ketoglutaric Acids / Q000378:metabolism; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D017862:Phycodnaviridae / Q000201:enzymology*; D011393:Procollagen-Proline Dioxygenase / Q000032:analysis* / Q000737:chemistry*; D015204:Spectroscopy, Mossbauer; D013379:Substrate Specificity; D017186:Titrimetry
chemical_list: D007656:Ketoglutaric Acids; D010455:Peptides; D002244:Carbon; D006859:Hydrogen; D007501:Iron; D006899:Mixed Function Oxygenases; D011393:Procollagen-Proline Dioxygenase