TY - JOUR
T1 - Dihydropterine reductase as an alternative to dihydrofolate reductase for synthesis of tetrahydrofolate in Thermus thermophilus
AU - Wilquet, Valérie
AU - Van De Casteele, M.
AU - Legrain, Christianne
AU - Glansdorff, Nicolas
PY - 2004/1
Y1 - 2004/1
N2 - A strategy to isolate a gene coding for a dihydrofolate reductase from Thermus thermophilus DNA delivered only clones harboring instead a gene (the T; thermophilus dehydrogenase (DHTt) gene) coding for a dihydropterine reductase which displays considerable dihydrofolate reductase activity (about 20% of the activity detected ith 6, 7)dimethyl-7,8-dihydropterine in the quinonoid form as a substrate). DHTt appears to account for the synthesis of dihydrofolate in this bacterium, since a classical dihydrofolate reductase gene could not be found in the recently determined genome nucleotide sequence (A. Henne, personal communication). The derived amino acid sequence displays most of the highly conserved cofactor and active-site residues present in th enzymes of the short-chain dehydrogenase/reductase family. The enzyme has no pterine-independent oxidoreductase activity, in contrast to Escherichia coli dihropterine reductase, and thus appears more similar to the mammalian dihydropterine reductases, which do not contain a flavin prosthetic group. We suggest that bifunctional dihydropterine reductases may be responsible for the synthesis of tetrahydrofolate in other bacteria, as well as archaea, that heve been reported to lack a classical difydrofolate reductase but for which possible substitutes have not yet been identified.
AB - A strategy to isolate a gene coding for a dihydrofolate reductase from Thermus thermophilus DNA delivered only clones harboring instead a gene (the T; thermophilus dehydrogenase (DHTt) gene) coding for a dihydropterine reductase which displays considerable dihydrofolate reductase activity (about 20% of the activity detected ith 6, 7)dimethyl-7,8-dihydropterine in the quinonoid form as a substrate). DHTt appears to account for the synthesis of dihydrofolate in this bacterium, since a classical dihydrofolate reductase gene could not be found in the recently determined genome nucleotide sequence (A. Henne, personal communication). The derived amino acid sequence displays most of the highly conserved cofactor and active-site residues present in th enzymes of the short-chain dehydrogenase/reductase family. The enzyme has no pterine-independent oxidoreductase activity, in contrast to Escherichia coli dihropterine reductase, and thus appears more similar to the mammalian dihydropterine reductases, which do not contain a flavin prosthetic group. We suggest that bifunctional dihydropterine reductases may be responsible for the synthesis of tetrahydrofolate in other bacteria, as well as archaea, that heve been reported to lack a classical difydrofolate reductase but for which possible substitutes have not yet been identified.
KW - dihydrofolate reductase
KW - dihydropterine reductase
KW - thermophiles
KW - Thermus thermophilus
M3 - Article
VL - 186
SP - 351
EP - 355
JO - Journal of Bacteriology
JF - Journal of Bacteriology
SN - 0021-9193
ER -