[Activation of leucine aminopeptidase under hydrogen bond cleaving conditions]

Cleavage of hydrogen bonds by urea, guanidinium chloride or elevated temperatures causes a reversible activation of leucine aminopeptidase. The activation is similar to that caused by Mg2+ ions. This means that preincubation is required and that a 10-fold or more activated enzyme is inhibited by 50 mM cyanide to 20 per cent while a C1-ion-activated enzyme like the nonactivated enzyme is inhibited to 90 per cent. Blockage of the free SH-groups reduces the response time of the activation. The free SH-groups are involved in an essential intermediate step of the activation.