Transforming a Stable Amide into a Highly Reactive One: Capturing the Essence of Enzymatic Catalysis.

Aspartic proteinases, which include HIV-1 proteinase, function with two aspartate carboxy groups at the active site. This relationship has been modeled in a system possessing an otherwise unactivated amide positioned between two carboxy groups. The model amide is cleaved at an enzyme-like rate that renders the amide nonisolable at 35 °C and pH 4 owing to the joint presence of carboxy and carboxylate groups. A currently advanced theory attributing almost the entire catalytic power of enzymes to electrostatic reorganization is shown to be superfluous when suitable interatomic interactions are present. Our kinetic results are consistent with spatiotemporal concepts where embedding the amide group between two carboxylic moieties in proper geometries, at distances less than the diameter of water, leads to enzyme-like rate enhancements. Space and time are the essence of enzyme catalysis.

Toxicity mechanisms of onion (Allium cepa) extracts and compounds in multidrug resistant erythroleukemic cell line.

Onion (Allium cepa) is being studied as a potential anticancer agent, but little is known regarding its effect in multidrug resistance (MDR) cells. In this work, the cytotoxicity of crude onion extract (OE) and fractioned extract (aqueous, methanolic and ethyl acetate), as well as some onion compounds (quercetin and propyl disulfide) were evaluated in Lucena MDR human erythroleukemic and its K562 parental cell line. The capacity of OE to induce apoptosis and/or necrosis in these cells, the possible participation of oxidative stress and DNA damage were also assessed. Similar sensitivities were obtained for both tumoral cells, however only OE caused significant effects in the cells. In K562 cells, a significant increase of apoptosis was verified while the Lucena cells experienced a significant increase of necrosis. An antioxidant capacity was verified for OE discarding oxidative damage. However, OE provoked similar significant DNA damage in both cell lines. Thus, the OE capacity to overcome the MDR phenotype suggests anti-MDR action of OE.

Toxicity mechanisms of onion (Allium cepa) extracts and compounds in multidrug resistant erythroleukemic cell line

Onion (Allium cepa) is being studied as a potential anticancer agent, but little is known regarding its effect in multidrug resistance (MDR) cells. In this work, the cytotoxicity of crude onion extract (OE) and fractioned extract (aqueous, methanolic and ethyl acetate), as well as some onion compounds (quercetin and propyl disulfide) were evaluated in Lucena MDR human erythroleukemic and its K562 parental cell line. The capacity of OE to induce apoptosis and/or necrosis in these cells, the possible participation of oxidative stress and DNA damage were also assessed. Similar sensitivities were obtained for both tumoral cells, however only OE caused significant effects in the cells. In K562 cells, a significant increase of apoptosis was verified while the Lucena cells experienced a significant increase of necrosis. An antioxidant capacity was verified for OE discarding oxidative damage. However, OE provoked similar significant DNA damage in both cell lines. Thus, the OE capacity to overcome the MDR phenotype suggests anti-MDR action of OE.

Perfil de ácidos graxos da pele e músculo de Balistes capriscus e Menticirrhus litoralis, pescados na região sul do Brasil / Fatty acids profile in muscle and skin of Balistes capriscus and Menticirrhus litoralis fished in southern region of Brazil

Neste trabalho foi determinado o perfil de ácidos graxos da pele e do músculo de duas espécies marinhas de pescados, Balistes capriscus e Menticirrhus littoralis, usadas pela população da região de Rio Grande no Rio Grande do Sul. Estes pescados foram selecionados pelos efeitos benéficos dos chás de suas peles para tratamento da asma brônquica. Os pescados foram coletados no mercado público e empresas de pescado da cidade e a pele e o músculo destes foram separados para o estudo. As frações lipídicas foram extraídas pelo método de Bligh e Dyer, esterificadas, identificadas e quantificadas por cromatografia gasosa. Os resultados revelaram que os ácidos graxos predominantes nas duas porções (músculo e pele)das espécies foram o ácido dihomo--linolênico (20:3n-6;DHA) e o ácido eicosapentaenóico (20:5n-3;EPA), estes representam juntos 21,3% e 39% nas duas porções do Balistes capriscus e 12,8% e 24,2%no Menticirrhus littoralis. Os ácidos graxos poliinsaturados representam de 54,6 a 67,6% dos lipídios totais em quase todas as porções, exceto na pele do Menticirrhus littoralis em que predominaram os ácidos graxos monoinsaturados. A relação dos ácidos graxos EPA e DHA apresentou valores sempre superiores a 2 no músculo e na pele dos pescados estudados.