Some observations on the inhibition and activation of a thermophilic protease

The activity of Caldolysin, the extracellular protease from the extreme thermophile Thermus aquaticus strain T351, was reduced in the presence of high protein concentrations. The absence of this effect after enzyme immobilization, or when using chromogenic substrates, suggests that a steric mechanism is involved. The apparent activation of caldolysin under certain conditions was shown to be related to both temperature and the ionic strength of the aqueous environment. The effects on activity, substrate affinity and thermostability of chemical modification with various reagents are also discussed.