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Applied and Environmental Microbiology, February 1999, p. 611-617, Vol. 65, No. 2
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Cold-Active Serine Alkaline Protease from the Psychrotrophic Bacterium Shewanella Strain Ac10: Gene Cloning and Enzyme Purification and Characterization

Ljudmila Kulakova, Andrey Galkin, Tatsuo Kurihara, Tohru Yoshimura, and Nobuyoshi Esaki*

Institute for Chemical Research, Kyoto University, Uji, Kyoto-Fu 611, Japan

Received 22 June 1998/Accepted 12 October 1998

The gene encoding serine alkaline protease (SapSh) of the psychrotrophic bacterium Shewanella strain Ac10 was cloned in Escherichia coli. The amino acid sequence deduced from the 2,442-bp nucleotide sequence revealed that the protein was 814 amino acids long and had an estimated molecular weight of 85,113. SapSh exhibited sequence similarities with members of the subtilisin family of proteases, and there was a high level of conservation in the regions around a putative catalytic triad consisting of Asp-30, His-65, and Ser-369. The amino acid sequence contained the following regions which were assigned on the basis of homology to previously described sequences: a signal peptide (26 residues), a propeptide (117 residues), and an extension up to the C terminus (about 250 residues). Another feature of SapSh is the fact that the space between His-65 and Ser-369 is approximately 150 residues longer than the corresponding spaces in other proteases belonging to the subtilisin family. SapSh was purified to homogeneity from the culture supernatant of E. coli recombinant cells by affinity chromatography with a bacitracin-Sepharose column. The recombinant SapSh (rSapSh) was found to have a molecular weight of about 44,000 and to be highly active in the alkaline region (optimum pH, around 9.0) when azocasein and synthetic peptides were used as substrates. rSapSh was characterized by its high levels of activity at low temperatures; it was five times more active than subtilisin Carlsberg at temperatures ranging from 5 to 15°C. The activation energy for hydrolysis of azocasein by rSapSh was much lower than the activation energy for hydrolysis of azocasein by the subtilisin. However, rSapSh was far less stable than the subtilisin.

* Corresponding author. Mailing address: Institute for Chemical Research, Kyoto University, Uji, Kyoto-Fu 611-0011, Japan. Phone: 81-774-38-3240. Fax: 81-774-38-3248. E-mail: esaki{at}scl.kyoto-u.ac.jp.

Applied and Environmental Microbiology, February 1999, p. 611-617, Vol. 65, No. 2
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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