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Media type:
E-Article
Title:
Physico‐Chemical Properties of Phosphatidylglycerol in Membranes of Acholeplasma laidlawii : A Study with Phospholipase A2
:
A Study with Phospholipase A<sub>2</sub>
Contributor:
BEVERS, Edouard M.;
OP DEN KAMP, Jos A. F.;
VAN DEENEN, Laurens L. M.
Published:
Wiley, 1978
Published in:
European Journal of Biochemistry, 84 (1978) 1, Seite 35-42
Description:
<jats:p>Membranes isolated from <jats:italic>Acholeplasma laidlawii</jats:italic> B grown on palmitic acid, elaidic acid, oleic acid or linoleic acid have been treated with excess phospholipase A<jats:sub>2</jats:sub> at different temperatures. Hydrolysis of phosphatidylglycerol only occurs at temperatures above the onset of the gel to liquid‐crystalline phase transition of the lipids as measured by differential scanning calorimetry. The extent of phosphatidylglycerol hydrolysis as a function of the temperature reflects the phase transition of this phospholipid in membranes of <jats:italic>A. laidlawii</jats:italic>.</jats:p><jats:p>Species analysis of the phosphatidylglycerol before and after treatment with phospholipase A<jats:sub>2</jats:sub> was carried out by double labeling techniques and fatty acid analysis. Phosphatidylglycerol isolated from cells grown on palmitic acid, predominantly consists of two different species: dipalmitoyl phosphatidylglycerol and monopalmitoyl phosphatidylglycerol in which only one of the two acyl chains is palmitic acid. The physical behaviour of both species in these membranes, as measured with phospholipase A<jats:sub>2</jats:sub>, resembles that of a monotectic system: at 25°C there is almost complete hydrolysis of the monopalmitoyl species, while all of the dipalmitoyl species, which is still in the highly ordered gel state, remains unhydrolyzed. This implies that the miscibility between lipids in the fluid and ordered domains is restricted.</jats:p><jats:p>When cells are grown on elaidic acid also two phosphatidylglycerol species are present, <jats:italic>i.e.</jats:italic> dielaidoyl phosphatidylglycerol and phosphatidylglycerol with one acyl chain different from elaidic acid (monoelaidoyl phosphatidylglycerol). Irrespective of the incubation temperature, there is little or no preferential hydrolysis of one of the phosphatidylglycerol species, as would be expected for a cocrystallizing system. In oleic‐acid‐enriched membranes the lipids exist in the liquid‐crystalline state in the temperature range from 0–40 °C. Information can be obtained only about a pool of phosphatidylglycerol which is protected against phospholipase attack at low temperature. This pool which comprises about 30–40% of the total phosphatidylglycerol mainly consists of monooleoyl phosphatidylglycerol.</jats:p>