Properties of glutamate dehydrogenase and its involvement in alanine production in a hyperthermophilic archaeon, Thermococcus profundus.

摘要: Thermococcus profundus, a hyperthermophilic archaeon, did not exhibit detectable glutamine synthetase activity, although the organism possessed an extraordinarily high level of glutamate dehydrogenase (GDH), content which reached over 10% total soluble proteins. This GDH was purified to homogeneity. The enzyme had molecular weight 263,000 and composed six homogeneous subunits 43,000. extremely thermostable with half life 1 h at 90 degrees C. Circular dichroism (CD) spectra revealed gradual unfolding alpha-helices upon exposure increasing temperature. reaction strongly biased toward formation. T. profundus excreted L-alanine into medium, concentration mM. High activity alanine aminotransferase (AAT) present in cells, while no detected. formation may be initiated by ammonia uptake followed aminotransfer from pyruvate AAT.