The pyrimidine nucleotide reductase step in riboflavin and F(420) biosynthesis in archaea proceeds by the eukaryotic route to riboflavin.
The Methanococcus jannaschii gene MJ0671 was cloned and overexpressed in Escherichia coli, and its gene product was tested for its ability to catalyze the pyridine nucleotide-dependent reduction of either 2,5-diamino-6-ribosylamino-4(3H)-pyrimidinone 5'-phosphate (compound 3) to 2,5-diamino-6-ribitylamino-4(3H)-pyrimidinone 5'-phosphate (compound 4) or 5-amino-6-ribosylamino-2,4(1H,3H)-pyrimidinedione 5'-phosphate (compound 7) to 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione 5'-phosphate (compound 5). Only compound 3 was found to serve as a substrate for the enzyme. NADPH and NADH functioned equally well as the reductants. This specificity for the reduction of compound 3 was also confirmed by using cell extracts of M. jannaschii and Methanosarcina thermophila. Thus, this step in riboflavin biosynthesis in these archaea is the same as that found in yeasts. The absence of the other genes in the biosynthesis of riboflavin in Archaea is discussed.
Graupner
Marion
M
Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0308, USA.
Xu
Huimin
H
White
Robert H
RH
D019843:Archaeal Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D017017:Methanococcus / Q000201:enzymology / Q000378:metabolism*; D011743:Pyrimidines / Q000378:metabolism; D012256:Riboflavin / Q000031:analogs & derivatives* / Q000096:biosynthesis*; D012264:Ribonucleotide Reductases / Q000378:metabolism*; D013379:Substrate Specificity
D019843:Archaeal Proteins; D011743:Pyrimidines; C007701:factor 420; D012264:Ribonucleotide Reductases; D012256:Riboflavin