title: Crystallographic snapshots of oxalyl-CoA decarboxylase give insights into catalysis by nonoxidative ThDP-dependent decarboxylases.
abstract: Despite more than five decades of extensive studies of thiamin diphosphate (ThDP) enzymes, there remain many uncertainties as to how these enzymes achieve their rate enhancements. Here, we present a clear picture of catalysis for the simple nonoxidative decarboxylase, oxalyl-coenzyme A (CoA) decarboxylase, based on crystallographic snapshots along the catalytic cycle and kinetic data on active site mutants. First, we provide crystallographic evidence that, upon binding of oxalyl-CoA, the C-terminal 13 residues fold over the substrate, aligning the substrate alpha-carbon for attack by the ThDP-C2 atom. The second structure presented shows a covalent reaction intermediate after decarboxylation, interpreted as being nonplanar. Finally, the structure of a product complex is presented. In accordance with mutagenesis data, no side chains of the enzyme are implied to directly participate in proton transfer except the glutamic acid (Glu-56), which promotes formation of the 1',4'-iminopyrimidine tautomer of ThDP needed for activation.
authors.affiliation: Department of Medical Biochemistry and Biophysics, Molecular Structural Biology, Karolinska Institutet, S-17177 Stockholm, Sweden.
authors.forename: Catrine L
authors.initials: CL
authors.lastname: Berthold
authors.forename: Cory G
authors.initials: CG
authors.lastname: Toyota
authors.forename: Patricia
authors.initials: P
authors.lastname: Moussatche
authors.forename: Martin D
authors.initials: MD
authors.lastname: Wood
authors.forename: Finian
authors.initials: F
authors.lastname: Leeper
authors.forename: Nigel G J
authors.initials: NG
authors.lastname: Richards
authors.forename: Ylva
authors.initials: Y
authors.lastname: Lindqvist
mesh_terms: D000214:Acyl Coenzyme A / Q000737:chemistry; D001665:Binding Sites; D002262:Carboxy-Lyases / Q000737:chemistry* / Q000235:genetics; D002384:Catalysis; D003065:Coenzyme A / Q000737:chemistry; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D009154:Mutation; D017510:Protein Folding; D011994:Recombinant Proteins / Q000737:chemistry; D013379:Substrate Specificity; D013835:Thiamine Pyrophosphate / Q000737:chemistry*
chemical_list: D000214:Acyl Coenzyme A; D011994:Recombinant Proteins; C523110:oxalyl-coenzyme A; C106238:formyl-coenzyme A; D002262:Carboxy-Lyases; C059418:oxalyl CoA decarboxylase; D013835:Thiamine Pyrophosphate; D003065:Coenzyme A