title: Structural and mechanistic studies on γ-butyrobetaine hydroxylase.
abstract: The final step in carnitine biosynthesis is catalyzed by γ-butyrobetaine (γBB) hydroxylase (BBOX), an iron/2-oxoglutarate (2OG) dependent oxygenase. BBOX is inhibited by trimethylhydrazine-propionate (THP), a clinically used compound. We report structural and mechanistic studies on BBOX and its reaction with THP. Crystallographic and sequence analyses reveal that BBOX and trimethyllysine hydroxylase form a subfamily of 2OG oxygenases that dimerize using an N-terminal domain. The crystal structure reveals the active site is enclosed and how THP competes with γBB. THP is a substrate giving formaldehyde (supporting structural links with histone demethylases), dimethylamine, malonic acid semi-aldehyde, and an unexpected product with an additional carbon-carbon bond resulting from N-demethylation coupled to oxidative rearrangement, likely via an unusual radical mechanism. The results provide a basis for development of improved BBOX inhibitors and may inspire the discovery of additional rearrangement reactions.
authors.affiliation: The Department of Chemistry and the Oxford Centre for Integrative Systems Biology, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX13TA, UK.
authors.forename: Ivanhoe K H
authors.initials: IK
authors.lastname: Leung
authors.forename: Tobias J
authors.initials: TJ
authors.lastname: Krojer
authors.forename: Grazyna T
authors.initials: GT
authors.lastname: Kochan
authors.forename: Luc
authors.initials: L
authors.lastname: Henry
authors.forename: Frank
authors.initials: F
authors.lastname: von Delft
authors.forename: Timothy D W
authors.initials: TD
authors.lastname: Claridge
authors.forename: Udo
authors.initials: U
authors.lastname: Oppermann
authors.forename: Michael A
authors.initials: MA
authors.lastname: McDonough
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Schofield
mesh_terms: D002331:Carnitine / Q000096:biosynthesis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D019281:Dimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity; D050563:gamma-Butyrobetaine Dioxygenase / Q000737:chemistry* / Q000378:metabolism
chemical_list: D050563:gamma-Butyrobetaine Dioxygenase; D002331:Carnitine