IMPROVEMENT OF THERMAL-STABILITY OF SUBTILISIN-J BY CHANGING THE PRIMARY AUTOLYSIS SITE

The thermostability of subtilisin J, an extracellular serine protease secreted from Bacillus stearothermophilus, has been improved by changi ng the primary autolysis site of the Asp-49 mutant protein. Previously we have shown that the Asp-49 mutant protein has proteolytic activity , but so unstable that it was primarily autolyzed in Tyr-58 Gln-59 pep tide bond during cultivation (Jang et al. Biochim. Biophys. Acta. 1162 , 233-235 1993). In the present study, to mitigate the autolytic degra dation and increase the thermostability, we deleted the Tyr-58 residue using the Asp-49 mutant as a template. This mutant (Asp-49/Delta Tyr- 58 mutant) protein showed an improved resistance to heat treatment wit hout changing the catalytic efficiency of the enzyme. These results sh ow that change of primary autolysis site can stabilize the subtilisin. (C) 1995 Academic Press, Inc.