Cysteine protease isoforms from Trypanosoma cruzi, cruzipain 2 and cruzain, present different substrate preference and susceptibility to inhibitors

Cysteine-proteinases from parasitic protozoa have been recently characteriz ed as factors of virulence and pathogenicity in several human and veterinar y diseases. In Chagas' disease, the chronic infection caused by Trypanosoma cruzi, structure-functional studies on cysteine proteases were thus far li mited to the parasite's major isoform, a cathepsin L-like lysosomal proteas e designated as cruzipain, cruzain or GP57/51. Encoded: by a large gene fam ily, cruzipain is efficiently targeted by synthetic inhibitors, which preve nt parasite intracellular growth and differentiation. We have previously de monstrated that the multicopy cruzipain gene family includes polymorphic se quences, which could encode functionally different isoforms. We report here a comparative kinetic study between cruzain, the archetype of the cruzipai n family, and an isoform, termed cruzipain 2, which is expressed preferenti ally by the mammalian stages of T. cruzi. Heterologous expression of the ca talytic domain of cruzipain 2 in Saccharomyces cerevisae yielded an enzyme that differs markedly from cruzain with respect to pH stability, substrate specificity and sensitivity to inhibition by natural and synthetic inhibito rs of cysteine proteases. We suggest that the structural-functional diversi fication imparted by genetic polymorphism or cruzipain genes may have contr ibuted to T. cruzi adaptation to vertebrate hosts. (C) 2001 Elsevier Scienc e B.V. All rights reserved.