Synergism between Phospholipase A and Various Peptides and SH-Reagents in Causing Haemolysis
The haemolytic action on washed guinea-pig red cells of the following substances has been studied: the direct lytic factor (DLF) of cobra venom, melittin and an apamin-containing fraction of bee venom, anaphylatoxin (AT), angiotensin, vasopressin, saponin, p-chloro-mercuribenzoate (p-CMB) and N-ethylmaleimide (NEM). Further the synergism of these substances with phospholipase A in causing haemolysis has been investigated.
In regard to the lytic effects, the substances studied can be classified as follows. 1. Substances which react with SH-groups, either by means of — S—S— bonds (DLF, apamin-fraction, AT, vasopressin) or by other structures (p-CMB, NEM) produce weak or no direct haemolysis, but strongly potentiate haemolysis caused by phospholipase A. Their effect is increased by Ca++ , inhibited by EDTA, and strongly dependent on temperature (as far as has been investigated). 2. Angiotensin, a peptide without disulfide groups, is not haemolytic, neither directly nor in combination with phospholipase A. Saponin, which does not react with SH-groups, also does not show potentiated haemolysis with phospholipase A in spite of being haemolytic itself. 3. Melittin, though not containing disulfide structures, does produce potentiated haemolysis with phospholipase A, even at concentrations which are not lytic when acting alone.
It is concluded that more than one mechanism of potentiating phospholipase A haemolysis exists. One possibility is the reaction of potentiating agents with SH-groups of membrane constituents (enzymes?) of the red cells. This mechanism applies to p-CMB, NEM and to disulfide-containing peptides. It is independent of detergent effects. Another mechanism may be membrane changes due to a lowering of surface tension such as that produced by melittin. It seems doubtful, however, whether this is the only molecular property responsible for the potentiation, as the detergent saponin does not have such an effect. Possibly melittin, in addition to having detergent effects interferes with the same membrane properties which are altered by the SH-reactants.
Key-WordsHaemolysis Phospholipase A Direct Lytic Factor Polypeptides Toxins
direct lytic factor (cobra venom
SchlüsselwörterHämolyse Phospholipase A Direkt lytischer Faktor Polypeptide Toxine
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