Novel Salt-Tolerant Leucine Dehydrogenase from Marine Pseudoalteromonas rubra DSM 6842

This study reported the cloning, expression, and characterization of a new salt-tolerant leucine dehydrogenase (PrLeuDH) from Pseudoalteromonas rubra DSM 6842. A codon-optimized 1038 bp gene encoding PrLeuDH was successfully expressed on pET-22b( +) in E. coli BL21(DE3). The purified recombinant PrLeuDH showed a single band of about 38.7 kDa on SDS-PAGE. It exhibited the maximum activity at 40 degrees C and pH 10.5, while kept high activities in the range of 25-45 degrees C and pH 9.5-12. The K-m value and turnover number k(cat) for leucine of PrLeuDH were 2.23 +/- 0.12 mM and 35.39 +/- 0.05 s(-1), respectively, resulting in a catalytic efficiency k(cat)/K-m of 15.87 s(-1)/mM. Importantly, PrLeuDH remained 92.1 +/- 2.67% active in the presence of 4.0 M NaCl. The study provides the first in-depth understanding of LeuDH from marine Pseudoalteromonas rubra, meanwhile the unique properties of high activity at low temperature and high salt tolerance make it a promising biocatalyst for the synthesis of non-protein amino acids and oc-ketoacids under special conditions in pharmaceutical industry.