Hemolisinas bacterianas / Bacterial hemolysins

RESUMO

Hemolytic activity has been reported in bacteria of different genera. They were associated with a cytotoxic effect on erythrocytes by means of membrane damage which can results in a rearragement and disruption of the bilayer; in this case, they are considred cytilysins. They action mechanism of a hemilysins group is done by phospholipase activity on hydrophobic regions of membranes, this enzymatic action causes a pertubation that lyses erythrocytes of different animal species. The behavior of other bacterial hemolysins tends to resemble that detergents, bacause they have a very strong activity on surface, they have relatively low hemolytic effect and exhibit a broad spectrum of sensitive cells, without preference for a particularerythrocyte species. A third group of hemolysins encloses the lysins activated by SH compounds, sometimes called "oxygen-labile emolysins", they share common properties; all of them are irreversibly inactivated by low concentrations of cholesterol, the oxygen effect can be abolished by reducing agents, they are inmunologically related to one another and the temperature reduces their activity. The SF form of these lysins is active. -S-S-form obtained by oxydation us ubactuve abd does not interact with erythrocytes. Cholesterol represents the primary lysin acceptor of membrane, but there are some differences among the thiol-dependent cystolysins in the reversibility of binding to membrane, the activity at -C and the damage caused in membranes with distinct leakage of cytoplasmic material ino the surrounding medium. The biggest group of hemolysins includes then lysins with an unknown mode of action, it comprises cytolysins of Gram-negative and Gram-positive bacteria. Althought the mechanisms of cell damage were studied by many investigators, the majority of hemolysins action mechanisms must be discovered. In the last years it was proposed that some bacterial lysins can act like other substances that pertub the membrane integrith by an important and very widespread mechanism of formation of transmembrane pores, with insertation of alien proteins into the lipid bilayer. When more hemolysins will be detected new characteistics and mode of actions will be more hemolysins will be detected new characteristics and mode of actions will be described, and the role if hemolysins in pathogeny will be best understood