Biosynthesis of riboflavin in archaea. 6,7-dimethyl-8-ribityllumazine synthase of Methanococcus jannaschii.
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Haase I, Mortl S, Kohler P, Bacher A, Fischer M
Biosynthesis of riboflavin in archaea. 6,7-dimethyl-8-ribityllumazine synthase of Methanococcus jannaschii.
Eur J Biochem. 2003 Mar;270(5):1025-32.
- PubMed ID
- 12603336 [ View in PubMed]
- 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.