ISOCITRATE DEHYDROGENASES FROM HALOFERAX-VOLCANII AND SULFOLOBUS-SOLFATARICUS - ENZYME-PURIFICATION, CHARACTERIZATION AND N-TERMINAL SEQUENCE

The isocitrate dehydroyenases from the extremely halophilic Archaeon, Haloferax volcanii, and from the hyperthermophilic Archaeon, Sulfolobu s solfataricus, have been purified to electrophoretic homogeneity. The purified enzymes have been characterised with respect to their cofact or specificities, subunit compositions and their salt and thermal stab ilities. N-terminal amino acid sequences have been determined for both enzymes, and multiple alignments with sequences of bacterial and euka ryotic isocitrate dehydrogenases show that the archaeal enzymes most c losely resemble the NADP-linked dimeric isocitrate dehydrogenases from the Bacteria.