title: Experimental observation of thiamin diphosphate-bound intermediates on enzymes and mechanistic information derived from these observations.
abstract: Thiamin diphosphate (ThDP), the vitamin B1 coenzyme, is an excellent representative of coenzymes, which carry out electrophilic catalysis by forming a covalent complex with their substrates. The function of ThDP is to greatly increase the acidity of two carbon acids by stabilizing their conjugate bases, the ylide/C2-carbanion of the thiazolium ring and the C2alpha-carbanion (or enamine) once the substrate binds to ThDP. In recent years, several ThDP-bound intermediates on such pathways have been characterized by both solution and solid-state (X-ray) methods. Prominent among these advances are X-ray crystallographic results identifying both oxidative and non-oxidative intermediates, rapid chemical quench followed by NMR detection of a several intermediates which are stable under acidic conditions, and circular dichroism detection of the 1',4'-imino tautomer of ThDP in some of the intermediates. Some of these methods also enable the investigator to determine the rate-limiting step in the complex series of steps.
authors.affiliation: Department of Chemistry, Rutgers University, Newark, NJ 07102, USA.
authors.forename: Frank
authors.initials: F
authors.lastname: Jordan
authors.forename: Natalia S
authors.initials: NS
authors.lastname: Nemeria
mesh_terms: D003067:Coenzymes / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004798:Enzymes / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D015394:Molecular Structure; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity; D013835:Thiamine Pyrophosphate / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D003067:Coenzymes; D004798:Enzymes; D009097:Multienzyme Complexes; D013835:Thiamine Pyrophosphate