RESUMO
Acute coronary syndromes (ACS), including unstable angina (UA) and acute myocardial infarction (MI), are clinical manifestations of a progressive atherosclerotic process. Antibodies (Ab) to heat shock proteins (hsp) have been reported to be associated with atherosclerosis. Blood samples from 35 patients with ACS and 20 healthy volunteers were tested for Ab to human hsp60 by an enzyme-linked immunosorbent assay (ELISA). Levels of specific serum Ab against hsp60 were significantly elevated in patients with ACS when compared to clinically healthy subjects. To determine the antigenic determinants recognized by these Ab, antibody binding to seven peptides, selected from the hydrophilic and acrophilic regions of the human hsp60 molecule, was assessed. Despite the individual variation in the immune response among patients, one immunodominant region was revealed corresponding to the hsp60 (409-424) peptide. The identification of this epitope may be important for understanding the function of this protein in the atherosclerotic process.
Assuntos
Angina Instável/imunologia , Autoanticorpos/sangue , Proteínas de Bactérias , Chaperonina 60/imunologia , Infarto do Miocárdio/imunologia , Fragmentos de Peptídeos/imunologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Sequência de Aminoácidos , Angina Instável/etiologia , Arteriosclerose/etiologia , Arteriosclerose/imunologia , Estudos de Casos e Controles , Chaperonina 60/genética , Chaperoninas/imunologia , Feminino , Humanos , Epitopos Imunodominantes/genética , Masculino , Pessoa de Meia-Idade , Dados de Sequência Molecular , Mycobacterium bovis/imunologia , Infarto do Miocárdio/etiologia , Fragmentos de Peptídeos/genéticaRESUMO
The smallest known naturally occurring trypsin inhibitor SFTI-1 (14 amino acid residues head-to-tail cyclic peptide containing one disulfide bridge) and its two analogues with one cycle each were synthesized by the solid phase method. Their trypsin inhibitory activity was determined as association equilibrium constants (K(a)). Additionally, hydrolysis rates with bovine beta-trypsin were measured. Among all three peptides, the wild SFTI-1 and the analogue with the disulfide bridge only had, within the experimental error, the same activity (the K(a) values 1.1 x 10(10) and 9.9 x 10(9) M(-1), respectively). Both peptides displayed unchanged inhibitory activity up to 6 h. The trypsin inhibitory activity of the analogue with the head-to-tail cycle only was 2.4-fold lower. It was also remarkably faster hydrolyzed (k = 1.1 x 10(-4) mol(peptide) x mol(enzyme)(-1) x s(-1)) upon the incubation with the enzyme than the other two peptides. This indicates that the head-to-tail cyclization is significantly less important than the disulfide bridge for maintaining trypsin inhibitory activity.
