Improvement of thermostability of cold-active serine alkaline protease from the psychrotrophic bacterium Shewanella sp strain Ac10 by rational mutagenesis

A serine alkaline protease (SapSh) from a psychrophilic bacterium Shewanella sp. strain Ac10 is a cold-active subtilase with low thermostability [Appl. Environ. Microbiol. 65 (1999) 611-617]. By means of homology modeling with other subtilase structures, we have constructed a mutant SapSh containing an extra salt bridge on its surface that exhibits higher thermostability and even higher V,(max)/K-m, (app) value than those of the wild-type SapSh. (C) 2003 Elsevier Science B.V. All rights reserved.