title: Interaction of proteinase inhibitors with phospholipid vesicles is modulated by pH.
abstract: rBbKI and rBbCI, plant recombinant inhibitors from Bauhinia bauhinioides, and BpuTI from Bauhinia purpurea seeds distinctly and specifically block proteolytic enzymes. The secondary structures of those inhibitors were compared and their interactions with phospholipid vesicles were evaluated by the release of calcein and by intrinsic fluorescence of tryptophan residues. The results show that rBbKI, rBbCI and BpuTI are able to interact with phospholipd vesicles and induce membrane permeabilization in a concentration- and pH-dependent manner. The leakage was rapid and extensive at pH 4.5, but at physiological pH, no calcein release was observed. These results may suggest that upon inflammation or microorganism invasion accompanied by lowering of pH, appropriate conditions may occur for the inhibitors to interact with cell membrane and act on specific proteolytic enzyme.
authors.affiliation: Departamento de Bioquímica, Universidade Federal de São Paulo-Escola Paulista de Medicina, Rua Três de Maio, 100 Vila Clementino, 04044-020 São Paulo, SP, Brazil.
authors.forename: Rosemeire A
authors.initials: RA
authors.lastname: Silva-Lucca
authors.forename: Henrique M S
authors.initials: HM
authors.lastname: Faneca
authors.forename: Maria C Pedroso
authors.initials: MC
authors.lastname: de Lima
authors.forename: Fernanda P
authors.initials: FP
authors.lastname: De Caroli
authors.forename: M L
authors.initials: ML
authors.lastname: Assis
authors.forename: Misako U
authors.initials: MU
authors.lastname: Sampaio
authors.forename: Maria Luiza V
authors.initials: ML
authors.lastname: Oliva
mesh_terms: D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D005452:Fluoresceins / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D010447:Peptide Hydrolases / Q000737:chemistry / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D011480:Protease Inhibitors / Q000737:chemistry / Q000378:metabolism*; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence; D034421:Sus scrofa; D013696:Temperature; D053835:Unilamellar Liposomes / Q000378:metabolism*
chemical_list: D005452:Fluoresceins; D010743:Phospholipids; D011480:Protease Inhibitors; D053835:Unilamellar Liposomes; D010447:Peptide Hydrolases; C007740:fluorexon