Dual catalytic apparatus of the thiamin diphosphate coenzyme: Acid-base via the 1 ',4 '-iminopyrimidine tautomer along with its electrophilic role

TitleDual catalytic apparatus of the thiamin diphosphate coenzyme: Acid-base via the 1 ',4 '-iminopyrimidine tautomer along with its electrophilic role
Publication TypeJournal Article
Year of Publication2003
AuthorsJordan, F, Nemeria NS, Zhang S, Yan Y, Arjunan P, Furey W
JournalJournal of the American Chemical Society
Volume125
Pagination12732-12738
Date PublishedOct
Type of ArticleArticle
ISBN Number0002-7863
Accession Numberhttp://apps.isiknowledge.com/InboundService.do?Func=Frame&product=WOS&action=retrieve&SrcApp=EndNote&Init=Yes&SrcAuth=ResearchSoft&mode=FullRecord&UT=000185990300032
KeywordsAMINO, AMINOPYRIMIDINE RING, ANGSTROM RESOLUTION, DECARBOXYLASE, DEPENDENT ENZYME, E1 SUBUNIT, ESCHERICHIA-COLI, GROUP, MULTIENZYME COMPLEX, PYRUVATE-DEHYDROGENASE COMPLEX, TRANSKETOLASE
Abstract

It was recently reported (Jordan, F.; Zhang, Z.; Sergienko, E. A. Bioorg. Chem. 2002, 30, 188198) that addition to the E477Q active-center variant of yeast pyruvate clecarboxylase of (a) pyruvate on a rapid-scan UV stopped-flow, or (b) acetaldehyde or benzoylformate on a circular dichroism (CD) instrument, generates a new band with lambda(max) near 300-310 nm. A chemical model demonstrated that the wavelength is appropriate to the 1',4'-iminopyrimidine tautomer of the 4'-aminopyrimidine ring in thiamin diphosphate. Herein, we report the formation of a new positive CD band centered at 305 nm when the Escherichia coli pyruvate dehydrogenase complex first El subunit and its variants are exposed to phosphonolactylthiamin diphosphate, a stable analogue of the covalent adduct formed between the substrate pyruvate and the C2 atom of thiamin diphosphate. The behavior of this CD band, whether it suggests saturation of the enzyme by phosphonolactylthiamin diphosphate, or its very existence (the band is not seen with the E571 A El variant, where E571 is hydrogen bonded to the N1' atom of the 4'-aminopyrimidine ring), as well as its position are consistent with its assignment to the 1',4'-imino thiamin diphosphate tautomer on the enzyme, chiral by virtue of its fixed V conformation. The mechanism of binding of phosphonolactylthiamin diphosphate closely resembles that of thiamin diphosphate itself.

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Alternate JournalJ. Am. Chem. Soc.