The cysteine peptidases of Trypanosoma cruzi: insights arising from the Genome Project.

KOSEC, G.; ALVAREZ, V.; CAZZULO, J.J.

Porotoroz, Eslovenia.

Conferencia; 5th International Conference on Cysteine Proteinases and Their Inhibitors: From structure to regulation and biology.; 2006

International Union of Biochemistry and Molecular Biology (IUBMB).

Trypanosoma cruzi, a flagellated protozoan parasite, which causes Chagas disease, contains several biochemically characterized proteolytic activities [1].  Other putative peptidases are predicted from the data of the recently completed genome project [2].  Predictions suggest the presence of 70 cysteine peptidases, 40 serine peptidases, 250 metallopeptidases (mostly homologues of leishmanolysin), 25 threonine peptidases, and 2 aspartyl peptidases, but the real total number may be near 200, since many alleles are reported as different genes. Clan CA is represented by 7 families.  The C1 family contains, in addition to the well characterized cruzipains 1 and 2 and cathepsin B [1],  2 other putative members, annotated as a cathepsin and a bromelain-like enzyme.   Family C2 (calpains) is represented by 24 sequences;  however, none of them has the calcium-binding domain, and only 2 have an intact catalytic triad, what makes unlikely that they are expressed as active enzymes. Families C12, C19 and C65 contain deubiquitinating enzymes, involved in the functioning of the 26S proteasome.  Two members of family C12 are present, and are expressed at least in some parasite stages. Family C19 is represented by a group a 18 considerably divergent homologues.   Family C65 is represented in T. cruzi by an otubain-1 homolog. Family C51 presents 5 sequences in the T. cruzi genome, annotated as putative D-alanyl-glicyl endopeptidases. Family C54 includes the Atg4 proteinases (autophagins).  Two homologues are present in the parasite;  we have recently expressed them and shown that they process correctly the T. cruzi Atg8 homologues, which participate in the formation of the autophagic vesicles.  Clan CD  is represented by families C13, C14  and C50.  Family C13 includes a T. cruzi homolog of the GPI transamidase.  Family C14 includes the metacaspases, presumably involved in apoptosis in lower eukaryotes and plants.  Two homologues,  TcMCA3 (16 copies)  and TcMCA5 (one copy per haploid genome) are present [3]    Family C50 is represented by one homolog of the separases, proteinases involved in the cleavage of the cohesin complex which maintains linked the sister chromatids during mitosis.  Clan CE is represented in T. cruzi by one member of the family C48, of the SUMOilases, involved in the deconjugation of the ubiquitin-like SUMO protein, which also has homologues in T. cruzi.   Clan CF is represented by one member of family C15, of the pyroglutamyl peptidase I, homologous to an enzyme expressed in Trypanosoma  brucei. [1]  J.J. Cazzulo (2002) Proteinases of Trypanosoma cruzi:  Potential targets for the chemotherapy of Chagas disease. Curr. Top. Med. Chem. 2, 1261 – 1271. [2]  N.M. El-Sayed et al. (2005) The genome sequence of Trypanosoma cruzi, etiologic agent of Chagas disease.  Science, 309, 409 – 415. [3]  G. Kosec et al. (2006)  Metacaspases of Trypanosoma  cruzi:  Possible candidates for programmed cell death mediators.  Mol. Biochem. Parasitol. 145, 18 – 28.