title: Characterization of the M32 metallocarboxypeptidase of Trypanosoma brucei: differences and similarities with its orthologue in Trypanosoma cruzi.
abstract: Metallocarboxypeptidases (MCP) of the M32 family of peptidases have been identified in a number of prokaryotic organisms but they are absent from eukaryotic genomes with the remarkable exception of those of trypanosomatids. The genome of Trypanosoma brucei, the causative agent of Sleeping Sickness, encodes one such MCP which displays 72% identity to the characterized TcMCP-1 from Trypanosoma cruzi. As its orthologue, TcMCP-1, Trypanosoma brucei MCP is a cytosolic enzyme expressed in both major stages of the parasite. Purified recombinant TbMCP-1 exhibits a significant hydrolytic activity against the carboxypeptidase B substrate FA (furylacryloil)-Ala-Lys at pH 7.0-7.8 resembling the T. cruzi enzyme. Several divalent cations had little effect on TbMCP-1 activity but increasing amounts of Co(2+) inhibited the enzyme. Despite having similar tertiary structure, both protozoan MCPs display different substrate specificity with respect to P1 position. Thus, TcMCP-1 enzyme cleaved Abz-FVK-(Dnp)-OH substrate (where Abz: o-aminobenzoic acid and Dnp: 2,4-dinitrophenyl) whereas TbMCP-1 had no activity on this substrate. Comparative homology models and sequence alignments using TcMCP-1 as a template led us to map several residues that could explain this difference. To verify this hypothesis, site-directed mutagenesis was undertaken replacing the TbMCP-1 residues by those present in TcMCP-1. We found that the substitution A414M led TbMCP-1 to gain activity on Abz-FVK-(Dnp)-OH, thus showing that this residue is involved in specificity determination, probably being part of the S1 sub-site. Moreover, the activity of both protozoan MCPs was explored on two vasoactive compounds such as bradykinin and angiotensin I resulting in two different hydrolysis patterns.
authors.affiliation: Instituto de Investigaciones Biotecnológicas Dr. Rodolfo Ugalde-Instituto Tecnológico Chascomús, UNSAM-CONICET, Campus Miguelete, Av. 25 de Mayo y Francia, 1650 San Martín, Buenos Aires, Argentina.
authors.forename: Alejandra P
authors.initials: AP
authors.lastname: Frasch
authors.forename: Adriana K
authors.initials: AK
authors.lastname: Carmona
authors.forename: Luiz
authors.initials: L
authors.lastname: Juliano
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Cazzulo
authors.forename: Gabriela T
authors.initials: GT
authors.lastname: Niemirowicz
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D002268:Carboxypeptidases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D020134:Catalytic Domain; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004151:Dipeptides / Q000737:chemistry; D004926:Escherichia coli; D031541:Fluorescence Resonance Energy Transfer; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008667:Metalloproteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011480:Protease Inhibitors / Q000737:chemistry; D059748:Proteolysis; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D040681:Structural Homology, Protein; D013379:Substrate Specificity; D028561:Transition Elements / Q000737:chemistry; D014346:Trypanosoma brucei brucei / Q000201:enzymology*; D014349:Trypanosoma cruzi / Q000201:enzymology*
chemical_list: D004151:Dipeptides; D008667:Metalloproteins; D011480:Protease Inhibitors; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D028561:Transition Elements; C028059:furylacryloylalanyllysine; D002268:Carboxypeptidases