Gene cloning, expression and characterization of a novel cold-adapted protease from Planococcus sp.

• A novel protease gene, cpls8, was cloned from the newly isolated bacterium and successfully expressed in Escherchia coli.
• The heterologously expressed CPLS8 exhibited optimal activity at pH 10.0 and demonstrated an increasing activity at temperatures between 5 and 35 °C with a complete inactivation at 55 °C.
• Compared with other cold-adapted proteases, the CPLS8 was more resistant to the detergent of SDS, which can keep more than 80% of the highest activity in the presence of SDS (1.0%), even the concentration of SDS is 3.0%, more than 19% of its initial activity was still retained.
• CPLS8 was a novel cold-adapted protease and seemed to be attractive for industrial application.

A psychrophilic bacterium strain named M7 was isolated from the deep-sea mud of Eastern Indian Ocean and identified as Planococcus sp. A novel protease gene, cpls8, was cloned from the newly isolated bacterium and successfully expressed in Escherchia coli. The open reading frame of cpls8 gene encodes a 329-amino acid polypeptide with a molecular weight of approximately 35.6 kDa. Sequence alignment reveals that the CPLS8 protease contains a catalytic module belonging to serralysin-type protease family 8 and displays the highest identity of 62% to a functionally known protease from Bacillus sp. The heterologously expressed CPLS8 exhibited optimal activity at pH 10.0 and demonstrated an increasing activity at temperatures between 5 and 35 °C with a complete inactivation at 55 °C. At 25 °C the relative activity of CPLS8 still reached to 80% of the highest activity at 35 °C. These enzymatic properties together with amino acid composition analysis showed that CPLS8 was a novel cold-adapted protease and seemed to be attractive for industrial application.

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