Bifunctional phosphoglucose/phosphomannose isomerase from the hyperthermophilic archaeon Pyrobaculum aerophilum.
ORF PAE1610 from the hyperthermophilic crenarchaeon Pyrobaculum aerophilum was first annotated as the conjectural pgi gene coding for hypothetical phosphoglucose isomerase (PGI). However, we have recently identified this ORF as the putative pgi/pmi gene coding for hypothetical bifunctional phosphoglucose/phosphomannose isomerase (PGI/PMI). To prove its coding function, ORF PAE1610 was overexpressed in Escherichia coli, and the recombinant enzyme was characterized. The 65-kDa homodimeric protein catalyzed the isomerization of both glucose-6-phosphate and mannose-6-phosphate to fructose-6-phosphate at similar catalytic rates, thus characterizing the enzyme as bifunctional PGI/PMI. The enzyme was extremely thermoactive; it had a temperature optimum for catalytic activity of about 100 degrees C and a melting temperature for thermal unfolding above 100 degrees C.
Institut für Allgemeine Mikrobiologie, Christian-Albrechts-Universität Kiel, Am Botanischen Garten 1-9, 24118 Kiel, Germany.
Thomas
T
Hansen
Claus
C
Urbanke
Peter
P
Schönheit
D019641:DNA, Archaeal / Q000235:genetics; D019281:Dimerization; D005956:Glucose-6-Phosphate Isomerase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature; D007700:Kinetics; D008359:Mannose-6-Phosphate Isomerase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008970:Molecular Weight; D010802:Phylogeny; D020836:Protein Structure, Quaternary; D041543:Pyrobaculum / Q000201:enzymology* / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D019641:DNA, Archaeal; D011994:Recombinant Proteins; D008359:Mannose-6-Phosphate Isomerase; D005956:Glucose-6-Phosphate Isomerase