RESUMO
Parasite-derived proteases are important for the parasite life cycle and the pathogenesis of the disease they produce. Proteases of intestinal protozoan parasite Blastocystis hominis were studied for the first time with azocasein assays and gelatin SDS-PAGE analysis. Parasitic lysates were found to have high protease activity and nine protease bands of low (20-33 kDa) and high (44-75 kDa) molecular weights were reported. Proteases were found to be pH-dependent and highest proteolytic activity was observed at neutral pH. Inhibition studies showed that B. hominis isolate B, like many other protozoan parasites, contains mainly cysteine proteases.
Assuntos
Blastocystis hominis/enzimologia , Peptídeo Hidrolases/metabolismo , Animais , Blastocystis hominis/efeitos dos fármacos , Cisteína Endopeptidases/metabolismo , Eletroforese em Gel de Poliacrilamida , Humanos , Peptídeo Hidrolases/efeitos dos fármacos , Inibidores de Proteases/farmacologiaRESUMO
Two new compounds, agonodepsides A (1) and B (2), were isolated from a nonsporulating filamentous fungus, F7524. The compounds were purified via reversed-phase chromatography and their structures determined by spectroscopic methods. Agonodepside A (1) was found to inhibit the mycobacterial InhA enzyme with an IC50 value of 75 microM, while 2 was inactive at 100 microM.
Assuntos
Fungos/química , Hidroxibenzoatos/isolamento & purificação , Proteínas de Bactérias , Depsídeos , Derris/química , Hidroxibenzoatos/química , Hidroxibenzoatos/farmacologia , Concentração Inibidora 50 , Testes de Sensibilidade Microbiana , Estrutura Molecular , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/enzimologia , NAD/efeitos dos fármacos , Ressonância Magnética Nuclear Biomolecular , Oxirredutases/efeitos dos fármacos , Folhas de Planta/química , Plantas/químicaRESUMO
The identification of small molecule inhibitors of antiapoptotic Bcl-2 family members has opened up new therapeutic opportunities, while the vast diversity of chemical structures and biological activities of natural products are yet to be systematically exploited. Here we report the identification of chelerythrine as an inhibitor of BclXL-Bak Bcl-2 homology 3 (BH3) domain binding through a high throughput screening of 107,423 extracts derived from natural products. Chelerythrine inhibited the BclXL-Bak BH3 peptide binding with IC50 of 1.5 micro m and displaced Bax, a BH3-containing protein, from BclXL. Mammalian cells treated with chelerythrine underwent apoptosis with characteristic features that suggest involvement of the mitochondrial pathway. While staurosporine, H7, etoposide, and chelerythrine released cytochrome c from mitochondria in intact cells, only chelerythrine released cytochrome c from isolated mitochondria. Furthermore BclXL-overexpressing cells that were completely resistant to apoptotic stimuli used in this study remained sensitive to chelerythrine. Although chelerythrine is widely known as a protein kinase C inhibitor, the mechanism by which it mediates apoptosis remain controversial. Our data suggest that chelerythrine triggers apoptosis through a mechanism that involves direct targeting of Bcl-2 family proteins.