Interaction of thiolsubtilisin with Streptomyces subtilisin inhibitor, SSI. |
| |
Authors: | K Fujiwara K Inouye B Tonomura S Murao D Tsuru |
| |
Abstract: | Subtilisin BPN' was chemically converted to thiolsubtilisin and the interaction of this modified enzyme with Streptomyces subtilisin inhibitor (SSI) was examined. SSI competitively inhibited the esterolytic activity of thiolsubtilisin toward p-nitrophenyl acetate with a K1 value of 1.3 X 10(-5) M at pH 7.5 Spectrophotometric analysis of the interaction between SSI and the modified enzyme yielded a Kd value of 4 X 10(-5) M at pH 9.7. These values are about 10(5)-fold greater than the Kd value (less than 10(-9) M at pH 7.5) for the native enzyme. This indicates that the small change in the active site structure of subtilisin (Ser221 to Cys221) leads to a considerable decrease in the binding affinity (by about 6-7 kcal/mol) to SSI. |
| |
Keywords: | |
|
|