title: Characterization of two D-glyceraldehyde-3-phosphate dehydrogenases from the extremely thermophilic archaebacterium Thermoproteus tenax.
abstract: Thermoproteus tenax possesses two different glyceraldehyde-3-phosphate dehydrogenases, one specific for NADP+ and the other for NAD+. NADP(H) inhibits the NAD+-specific enzyme competetively with respect to NAD+ whereas NAD(H) virtually does not interact with the NADP+-specific enzyme. Both enzymes represent homomeric tetramers with subunit molecular masses of 39 kDa (NADP+-specific enzyme) and 49 kDa (NAD+-specific enzyme), respectively. The NADP+-specific enzyme shows significant homology to the known glyceraldehyde-3-phosphate dehydrogenases from eubacteria and eukaryotes as indicated by partial sequencing. The enzymes are thermostable, the NADP+-specific enzyme with a half-life of 35 min at 100 degrees C, the NAD+-specific enzyme with a half-line of greater than or equal to 20 min at 100 degrees C, depending on the protein concentration. Both enzymes show conformational and functional changes at 60-70 degrees C.
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001105:Archaea / Q000201:enzymology*; D001419:Bacteria / Q000201:enzymology*; D004795:Enzyme Stability; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000302:isolation & purification / Q000378:metabolism*; D006358:Hot Temperature; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010084:Oxidation-Reduction; D013045:Species Specificity; D013816:Thermodynamics
chemical_list: D000596:Amino Acids; D007527:Isoenzymes; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases