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Glyceraldehyde-3-phosphate ferredoxin oxidoreductase (GAPOR) and nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase (GAPN), key enzymes of the respective modified Embden-Meyerhof pathways in the hyperthermophilic crenarchaeota Pyrobaculum aerophilum and Aeropyrum pernix

Reher, Matthias, Gebhard, Susanne, Schönheit, Peter
FEMS microbiology letters 2007 v.273 no.2 pp. 196-205
6-phosphofructokinase, acetaldehyde, enzyme activity, formaldehyde, fructose-bisphosphate aldolase, genes, glucokinase, glucose-6-phosphate isomerase, glyceraldehyde, glyceraldehyde 3-phosphate, glyceraldehyde-3-phosphate dehydrogenase, maltose, nitrates, open reading frames, phosphopyruvate hydratase, pyruvate kinase, thermal stability, triose-phosphate isomerase, yeast extract, yeasts
The growth of Pyrobaculum aerophilum on yeast extract and nitrate was stimulated by the addition of maltose. Extracts of maltose/yeast extract/nitrate-grown cells contained all enzyme activities of a modified Embden-Meyerhof (EM) pathway, including ATP-dependent glucokinase, phosphoglucose isomerase, ATP-dependent 6-phosphofructokinase, fructose-1,6-phosphate aldolase, triose-phosphate isomerase, GAPOR, phosphoglycerate mutase, enolase and pyruvate kinase. The activity of GAPOR was stimulated about fourfold by maltose, indicating a role in sugar degradation. GAPOR was purified 200-fold to homogeneity and characterized as a 67 kDa monomeric, extremely thermostable protein. The enzyme showed high specificity for glyceraldehyde-3-phosphate and did not use glyceraldehyde, acetaldehyde or formaldehyde as substrates. By matrix-assisted laser desorption/ionization-time of flight analysis of the purified enzyme, ORF PA1029 was identified as a coding gene, gapor, in the sequenced genome of Pyrobaculum aerophilum. The data indicate that the (micro)aerophilic Pyrobaculum aerophilum contains a functional GAPOR as part of a modified EM pathway. Cells of the strictly aerobic crenarchaeon Aeropyrum pernix also contain enzyme activities of a modified EM pathway similar to that of Pyrobaculum aerophilum, except that a GAPN activity replaces GAPOR activity.