Characterization of native glutamate dehydrogenase from an aerobic hyperthermophilic archaeon Aeropyrum pernix K1

Glutamate dehydrogenase (GDH) was purified and characterized from an aerobi c hyperthermophilic archaeon Aeropyrum pernix (A. pernix) K1. The enzyme ha s a hexameric structure with a native molecular mass of about 285 +/- 15 kD a. It was specific for NADP and thermostable (74% activity was remained aft er 5 h incubation at 100 degreesC). The activity of the enzyme increased in the presence of polar water-miscible organic solvents such as acetonitrile , methanol, and ethanol. The N-terminal sequence of GDH is Met-Gln-Pro-Thr- Asp-Pro-Leu-Glu-Glu-Ala. This sequence, except for the methionine, correspo nds to amino acids 7-15 of the open reading frame (ORF) encoding the predic ted GDH (ORF APE 1386). In the ORF nucleotide sequence, the codon TTG appea rs at the position of the methionine, suggesting that the leucine codon mig ht be recognized as an initiation codon and translated to methionine in A. pernix GDH.