SUBSTRATE-INHIBITION OF CRUZIPAIN IS NOT AFFECTED BY THE C-TERMINAL DOMAIN

Endogenous and rccombinant cruzipain, the major cysteine proteinase fr om the protozoan parasite Trypanosoma cruzi, exhibit differences in th e protein and circular dichroism spectra probably attributed to the ab sence of the C-terminal domain in the recombinant enzyme. Substrate hy drolysis of both molecules at 25 degrees C and neutral pH obeyed Micha elis-Menten kinetics,whereas significant substrate inhibition was obse rved above neutral pH. The results suggest that substrate inhibition o f cruzipain is pH-dependent, and that the C-terminal domain does not p lay an essential role in this process. (C) 1998 Federation of European Biochemical Societies.