Substrate-dependent Activation of Thermolysin by Salt

Abstract

Salt-activation of thermolysin was examined using a positively charged fluorescent substrate, (7-methoxycoumarin-4-yl)acetyl-L-Pro-L-Leu-Gly-L-Leu-[N³-(2,4-dinitrophenyl)-L-2,3-diaminopropionyl]-L-Ala-L-Arg-NH₂ [MOCAc-PLGL(Dpa)AR]. Thermolysin activity increased in a biphasic exponential fashion and was 40 times higher in the presence of 4 M NaCl than in its absence. The degree of activation at x M NaCl was expressed as 4.7^x when [NaCl]_o<0.5 M and 2.3^x when [NaCl]_o>0.5 M respectively.