title: Biosynthesis of vitamin B2: diastereomeric reaction intermediates of archaeal and non-archaeal riboflavin synthases.
abstract: The dismutation of 6,7-dimethyl-8-ribityllumazine catalyzed by riboflavin synthase affords riboflavin and 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione. A pentacyclic adduct of two 6,7-dimethyl-8-ribityllumazines has been identified earlier as a catalytically competent reaction intermediate of the Escherichia coli enzyme. Acid quenching of reaction mixtures of riboflavin synthase of Methanococcus jannaschii, a paralog of 6,7-dimethyl-8-ribityllumazine synthase devoid of similarity with riboflavin synthases of eubacteria and eukaryotes, afforded a compound whose optical absorption and NMR spectra resemble that of the pentacyclic E. coli riboflavin synthase intermediate, whereas the circular dichroism spectra of the two compounds have similar envelopes but opposite signs. Each of the compounds could serve as a catalytically competent intermediate for the enzyme by which it was produced, but not vice versa. All available data indicate that the respective pentacyclic intermediates of the M. jannaschii and E. coli enzymes are diastereomers.
authors.affiliation: Lehrstuhl für Organische Chemie und Biochemie, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany.
authors.forename: Boris
authors.initials: B
authors.lastname: Illarionov
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Eisenreich
authors.forename: Nicholas
authors.initials: N
authors.lastname: Schramek
authors.forename: Adelbert
authors.initials: A
authors.lastname: Bacher
authors.forename: Markus
authors.initials: M
authors.lastname: Fischer
mesh_terms: D001105:Archaea / Q000201:enzymology*; D019843:Archaeal Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000378:metabolism; D017013:Methanobacteriaceae / Q000201:enzymology*; D012256:Riboflavin / Q000096:biosynthesis* / Q000737:chemistry; D012258:Riboflavin Synthase / Q000378:metabolism*; D013237:Stereoisomerism
chemical_list: D019843:Archaeal Proteins; D029968:Escherichia coli Proteins; D012258:Riboflavin Synthase; D012256:Riboflavin