Hallophile aldehyde dehydrogenase from Halobacterium salinarum

Halobacterium salinarum is a member of the halophilic archaea. In the present study, H. salinarum was cultured at various NaCl concentrations (3.5, 4.3, and 6.0 M NaCl), and its proteome was determined and identificated via proteomics technique. We detected 14 proteins which were significantly down-regulated in 3.5 M and/or 6 M NaCl. Among the identified protein spots, aldehyde dehydrogenase (ALDH) was selected for evaluation with regard to its potential applications in industry. The most effective metabolism function exhibited by ALDH is the oxidation of aldehydes to carboxylic acids. The ALDH gene from H. salinarum (1.5 kb fragment) was amplified by PCR and cloned into the E. coli strain, BL21 (DE3), with the pGEX-KG vector. We subsequently analyzed the enzyme activity of the recombinant ALDH (54 kDa) at a variety of salt concentrations. The purified recombinant ALDH from H. salinarum exhibited the most pronounced activity at 1 M NaCl. Therefore, the ALDH from H. salinarum is a halophilic enzyme, and may prove useful for applications in hypersaline environments.