Enzymological Characteristics of the Hyperthermostable NAD- Dependent Glutamate Dehydrogenase from the Archaeon Pyrobaculum islandicum and Effects of Denaturants and Organic Solvents

摘要: During the past decade, many anaerobic hyperthermophiles growing at a temperature near or above boiling point of water have been isolated from marine and continental volcanic environments (1). The interest in has rapidly expanding. In particular, is focused on understanding adaptation mechanisms that allow metabolism to function biomolecules, such as protein, enzyme, DNA, remain intact extremely high temperature. Most belong Archaea, third domain life (22), evolutionary attention paid their biomolecules because they may be most slowly evolving primitive group microorganisms yet discovered. addition, enzymes large biotechnological potential (2, 6). Of hyperthermophiles, glutamate dehydrogenase (GluDH) (EC 1.4.1.4., glutamate:NADP oxidoreductase) one for which abundant information concerning enzymological properties relationships between structure obtained. Extremely thermostable NADP-dependent GluDHs purified Pyrococcus furiosus (5, 18, 20), woesei (18), Thermococcus litoralis (14, 19), profundus (11). gdhA gene (8, 9) cloned sequenced, structural difference furiosus, T. litoralis, Clostridium symbiosum investigated elucidate protein thermostability (3). key role ion pair networks maintaining stability GluDH an indicated (24). However, about hyperthermostable limited so far regarding hyperthermophilic species order Thermococcales Thermococcus. In course investigating distribution archaea, we found activity NAD-dependent 1.4.1.2) cell extract archaeon, Pyrobaculum islandicum. This first example occurrence archaea. general, physiological known different (17). expected more preferable application than NAD NADH are much cheaper NADP NADPH, respectively (4, 23). Thus, enzyme P. islandicum characterization. We describe here characteristics this with emphasis its some denaturants organic solvents.