Molecular Characterization of the Iron-Containing Alcohol Dehydrogenase from the Extremely Thermophilic Bacterium <i>Pseudothermotoga hypogea</i>
2024
Liangliang Hao | Zainab Ayinla | Kesen Ma
<i>Pseudothermotoga hypogea</i> is an extremely thermophilic bacterium capable of growing at 90 °C and producing ethanol, which is catalyzed by an alcohol dehydrogenase (ADH). The gene encoding <i>P. hypogea</i> ADH (<i>Ph</i>ADH) was cloned, sequenced and over-expressed. The gene sequence (1164 bp) was obtained by sequencing all fragments of the gene, which were amplified from the genomic DNA. The deduced amino acid sequence showed high identity to iron-containing ADHs from other <i>Thermotoga</i> species and harbored typical iron- and NADP-binding motifs, Asp195His199His268His282 and Gly39Gly40Gly41Ser42, respectively. Structural modeling showed that the N-terminal domain of <i>Ph</i>ADH contains an α/β-dinucleotide-binding motif and that its C-terminal domain is an α-helix-rich region containing the iron-binding motif. The recombinant <i>Ph</i>ADH was soluble, active, and thermostable, with a subunit size of 43 ± 1 kDa revealed by SDS-PAGE analyses. The recombinant <i>Ph</i>ADH (69 ± 2 U/mg) was shown to have similar properties to the native enzyme. The optimal pH values for alcohol oxidation and aldehyde reduction were 11.0 and 8.0, respectively. It was also thermostable, with a half-life of 5 h at 70 °C. The successful expression of the recombinant <i>Ph</i>ADH in <i>E. coli</i> significantly enhanced the yield of enzyme production and thus will facilitate further investigation of the catalytic mechanisms of iron-containing ADHs.
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