title: Structure of cruzipain/cruzain inhibitors isolated from Bauhinia bauhinioides seeds.
abstract: The saline extract of Bauhinia bauhinioides dry seeds was shown to inhibit cruzipain, a cysteine proteinase from Trypanosoma cruzi. The inhibitory activity was assigned to a protein with 164 amino acid residues and molecular mass of 18 034 Da that was purified by chromatography on DEAE-Sephadex, trypsin-Sepharose (removal of trypsin inhibitors), Mono Q and a reversed-phase C4 column. The primary structure is homologous to other plant Kunitz-type inhibitors, but it lacks cysteine residues and therefore the disulfide bridges. No methionine residue was identified by amino acid sequencing. The inhibition of cruzipain fits into a slow-tight binding mechanism with a low dissociation constant (Ki 1.2 nM). The studied Bauhinia protein also inhibits cruzain (Ki 0.3 nM), a C-terminally truncated recombinant species of cruzipain. Cathepsin L, a cysteine proteinase with high homology to cruzipain, is also inhibited (Ki 0.22 nM), but not cathepsin B, papain, bromelain or ficin.
authors.affiliation: Department of Biochemistry, Universidade Federal de São Paulo, Escola Paulista de Medicina, SP, Brazil.
authors.forename: C
authors.initials: C
authors.lastname: de Oliveira
authors.forename: L A
authors.initials: LA
authors.lastname: Santana
authors.forename: A K
authors.initials: AK
authors.lastname: Carmona
authors.forename: M H
authors.initials: MH
authors.lastname: Cezari
authors.forename: M U
authors.initials: MU
authors.lastname: Sampaio
authors.forename: C A
authors.initials: CA
authors.lastname: Sampaio
authors.forename: M L
authors.initials: ML
authors.lastname: Oliva
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003546:Cysteine Endopeptidases / Q000187:drug effects / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry* / Q000302:isolation & purification; D007700:Kinetics; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors*; D012639:Seeds / Q000737:chemistry; D016415:Sequence Alignment
chemical_list: D015853:Cysteine Proteinase Inhibitors; D010940:Plant Proteins; D015800:Protozoan Proteins; D003546:Cysteine Endopeptidases; C074032:cruzain, Trypanosoma cruzi; C063214:cruzipain