Intrinsic differences in the perturbing ability of alkanols in bilayer: Action of phospholipase A2 on the alkanol-modified phospholipid bilayer

Upreti, G.C.; Rainier, Shirley; Jain, Mahendra Kumar

doi:10.1007/bf01871152

Cited by 38 publications

(19 citation statements)

References 24 publications

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“…The action of phospholipase A2 (bee venom) on phospholipid bilayers is facilitated several hundredfold by a variety of additives [3,12,13]. We have shown [13] that the activating effect of alkanols is related to the free space introduced by alkanols in the bilayers.…”

Section: Introductionmentioning

confidence: 96%

Action of phospholipase A2 on unmodified phosphatidylcholine bilayers: Organizational defects are preferred sites of action

Upreti

Jain

1980

J. Membrain Biol.

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The hydrolytic action of the bee venom phospholipase A2 on phosphatidylcholine bilayers is studied under a variety of conditions that introduce alterations in the packing, such as those induced by sonication, gel to liquid crystalline phase transition, and osmotic shock. Two phases of hydrolysis could be resolved under a wide range of experimental conditions. With the various forms of the bilayers one observes only a partial hydrolysis of the total available substrate during the first phase. However, the fraction of the substrate hydrolyzed in the first phase changes with the form of the available substrate, with the amount of the enzyme added, with the temperature, with the phase transition characteristics of the substrate, and by the sonication of the substrate. The second phase of hydrolysis is generally observed when a certain concentration of the products has been produced during the first phase of hydrolysis. These obervations are interpreted to suggest that the bee venom phospholipase A2 preferentially catalyzes hydrolysis of the substrate available at or near the defects in the organization of the substrate in the bilayers.

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Section: Introductionmentioning

confidence: 96%

Action of phospholipase A2 on unmodified phosphatidylcholine bilayers: Organizational defects are preferred sites of action

Upreti

Jain

1980

J. Membrain Biol.

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“…The results show that the lytic enhancement by the cis isomer was much greater than that by the trans isomer (Fig. 5), as would be expected from their respective membrane-disordering capacities (24). Because the initial dispersion ofthe alcohols contained a small quantity of chloroform (1/2000), a control experiment with a similar dispersion ofchloroform in buffer was performed.…”

Section: Resultsmentioning

confidence: 71%

“…Equal volumes of erythrocytes (3 x 108 per ml of NaCl/B) and alcohol dispersions at the desired concentrations were incubated for 2 hr at 37°C. Under these conditions, near complete uptake of Relative concentration of C5b6 the alcohols into the erythrocyte membrane is expected because the partition coefficients of these long chain alcohols are extremely high (24). Accordingly, when erythrocytes were treated with supernatants of the initial incubation, no lytic enhancement by CMb-9 was observed.…”

Section: Resultsmentioning

confidence: 99%

“…Like A2C (17,21,22), cis unsaturated aliphatic alcohols promote membrane disorder (18,23,24). Accordingly, a comparison was made between the capacity ofthe cis and trans isomers of C14:1 alcohols to affect lysis by C5b-9.…”

Section: Resultsmentioning

confidence: 99%

“…It has been shown that incorporation of A2C into membranes produces disorder in the bilayer packing (17,21,22,24 (21,22). Also, altered distribution of human erythrocytes inatwo-phasedextran/polyethylene glycol/ water system has been reported (22).…”

Section: Discussionmentioning

confidence: 99%

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Effect of agents that produce membrane disorder on lysis of erythrocytes by complement.

Shin¹,

Hänsch²,

Mayer³

1981

Proc. Natl. Acad. Sci. U.S.A.

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To evaluate the effect of membrane lipid acylchain packing on the efficiency of cell lysis by complement, we have studied membrane modulation by 2-(2-methoxy)-ethoxyethyl-8-(cis-2-n-octylcyclopropyl)-octanoate (A2C) and by myristoleyl alcohol, the cis isomer of a C14:1 aliphatic alcohol. These substances are known to increase the membrane lipid disorder by virtue of the bend in their acyl chains, which is believed to loosen the phospholipid acyl-chain packing. We have found that both of these compounds markedly enhance the lysis of erythrocytes by the terminal complement proteins C5b-9. The enhancing effect by A2C is operative in the formation oferythrocytes carrying complement components C5b, C6, and C7, as well as in the subsequent reactions with complement components C8 and C9. We have also found that A2C-treated erythrocytes bind C5b6 to a measurable extent, whereas untreated erythrocytes do not. We attribute this to a shift in the partition equilibrium of C5b6 toward membrane association, which would improve lytic efficiency. The increase of membrane lipid disorder by these agents would also be expected to increase insertion of hydrophobic peptides from C7, C8, and C9, with consequent gain in lytic efficiency. Treatment of erythrocytes with sublytic doses of NaDodSO4 or Triton X-100 did not enhance lysis by C5b-9 appreciably, suggesting that enhancement of lysis by C5b-9 is not a general property of amphiphiles. Membrane attack by complement (C) is initiated when the com-.ponent C5 is cleaved into C5a and C5b by the C5 convertases of either the classical or alternative activation pathways. The subsequent interactions among the terminal complement proteins (C5b-C9) are accompanied by exposure of hydrophobic peptides (1-3). If this occurs in the immediate vicinity of a bilayer membrane, some ofthe exposed peptides became inserted in the lipid bilayer (4-6) and are assembled into channels that permit ion flow across the membrane (7-11). In the case ofcells that are susceptible to colloid-osmotic disruption, this leads to cytolysis. The processes of insertion and channel formation are affected by the chemical properties of the membrane (12)(13)(14)(15)(16) Chemicals. A2C (Makor, Jerusalem, Israel) was dispersed in 5 mM sodium barbital/142 mM sodium chloride, pH 7.4 (NaCl/ B). This dispersion was sonicated in a bath sonicator at room temperature until a homogeneous turbid colloidal suspension was obtained ('-3-5 min). Initially, 2 ,ul of A2C was dispersed in 5 ml of the NaCl/B to make a 0.1% stock suspension.Myristoleyl alcohol (Sigma) or its trans isomer (Nu Check Prep, Elysian, MN) (an unsaturated bond at C7-C8 position) were dissolved in chloroform to a concentration of 1%. This solution was mixed with NaCl/B and sonicated with a 1-cm diameter probe at a 40% power setting (Biosonick IV) for 3-5 min at 0°C.Triton X-100 (Sigma) or NaDodSO4 (BDH, Poole, England) were dissolved initially in NaCl/B to final concentrations of0.1 and 0.05 mM, and further dilutions were later made to determine the sublytic c...

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Phospholipase A₂ at the bilayer interface

Ramírez¹,

Jain²

1991

Proteins

162

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Interfacial catalysis is a necessary consequence for all enzymes that act on amphipathic substrates with a strong tendency to form aggregates in aqueous dispersions. In such cases the catalytic event occurs at the interface of the aggregated substrate, the overall turnover at the interface is processive, and it is influenced the molecular organization and dynamics of the interface. Such enzymes can access the substrate only at the interface because the concentration of solitary monomers of the substrate in the aqueous phase is very low. Moreover, the microinterface between the bound enzyme and the organized substrate not only facilitates formation of the enzyme-substrate complex, but a longer residence time of the enzyme at the substrate interface also promotes high catalytic processivity. Binding of the enzyme to the substrate interface as an additional step in the overall catalytic turnover permits adaptation of the Michaelis-Menten formalism as a basis to account for the kinetics of interfacial catalysis. As shown for the action of phospholipase A2 on bilayer vesicles, binding equilibrium has two extreme kinetic consequences. During catalysis in the scooting mode the enzyme does not leave the surface of the vesicle to which it is bound. On the other hand, in the hopping mode the absorption and desorption steps are a part of the catalytic turnover. In this minireview we elaborate on the factors that control binding of pig pancreatic phospholipase A2 to the bilayer interface. Binding of PLA2 to the interface occurs through ionic interactions and is further promoted by hydrophobic interactions which probably occur along a face of the enzyme, with a hydrophobic collar and a ring of cationic residues, through which the catalytic site is accessible to substrate molecules in the bilayer. An enzyme molecule binds to the surface occupied by about 35 lipid molecules with an apparent dissociation constant of less than 0.1 pM for the enzyme on anionic vesicles compared to 10 mM on zwitterionic vesicles. Results at hand also show that aggregation or acylation of the protein is not required for the high affinity binding or catalytic interaction at the interface.

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Intrinsic differences in the perturbing ability of alkanols in bilayer: Action of phospholipase A2 on the alkanol-modified phospholipid bilayer

Cited by 38 publications

References 24 publications

Action of phospholipase A2 on unmodified phosphatidylcholine bilayers: Organizational defects are preferred sites of action

Action of phospholipase A2 on unmodified phosphatidylcholine bilayers: Organizational defects are preferred sites of action

Effect of agents that produce membrane disorder on lysis of erythrocytes by complement.

Phospholipase A₂ at the bilayer interface

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Intrinsic differences in the perturbing ability of alkanols in bilayer: Action of phospholipase A2 on the alkanol-modified phospholipid bilayer

Cited by 38 publications

References 24 publications

Action of phospholipase A2 on unmodified phosphatidylcholine bilayers: Organizational defects are preferred sites of action

Action of phospholipase A2 on unmodified phosphatidylcholine bilayers: Organizational defects are preferred sites of action

Effect of agents that produce membrane disorder on lysis of erythrocytes by complement.

Phospholipase A2 at the bilayer interface

Contact Info

Product

Resources

About

Phospholipase A₂ at the bilayer interface