title: Biosynthesis of riboflavin in archaea. 6,7-dimethyl-8-ribityllumazine synthase of Methanococcus jannaschii.
abstract: Heterologous expression of the putative open reading frame MJ0303 of Methanococcus jannaschii provided a recombinant protein catalysing the formation of the riboflavin precursor, 6,7-dimethyl-8-ribityllumazine, by condensation of 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione and 3,4-dihydroxy-2-butanone 4-phosphate. Steady state kinetic analysis at 37 degrees C and pH 7.0 indicated a catalytic rate of 11 nmol.mg-1.min-1; Km values for 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione and 3,4-dihydroxybutanone 4-phosphate were 12.5 and 52 micro m, respectively. The enzyme sediments at an apparent velocity of about 12 S. Sedimentation equilibrium analysis indicated a molecular mass around 1 MDa but was hampered by nonideal solute behaviour. Negative-stained electron micrographs showed predominantly spherical particles with a diameter of about 150 A. The data suggest that the enzyme from M. jannaschii can form capsids with icosahedral 532 symmetry consisting of 60 subunits.
authors.affiliation: Lehrstuhl für Organische Chemie und Biochemie, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany.
authors.forename: Ilka
authors.initials: I
authors.lastname: Haase
authors.forename: Simone
authors.initials: S
authors.lastname: Mörtl
authors.forename: Peter
authors.initials: P
authors.lastname: Köhler
authors.forename: Adelbert
authors.initials: A
authors.lastname: Bacher
authors.forename: Markus
authors.initials: M
authors.lastname: Fischer
mesh_terms: D000595:Amino Acid Sequence; D017017:Methanococcus / Q000201:enzymology / Q000378:metabolism*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D012256:Riboflavin / Q000096:biosynthesis*; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization; D014461:Ultracentrifugation
chemical_list: D009097:Multienzyme Complexes; C044822:6,7-dimethyl-8-ribityllumazine synthase; D012256:Riboflavin