Abstract
Summary: Phospholipases A1 and A2 from rabbit lung lysosomes have maximal activity at pH 4.0 (Fig. 1). Lamellar bodies from rabbit lung contain phospholipases A which resemble the lysosomal enzymes in being active at pH 4 and showing sensitivity to inhibition by calcium ions (80% inhibition at 10 mM Ca2+). Lamellar body phospholipases hydrolyse dipalmitoyl phosphatidylcholine (containing 10% phosphatidylglycerol and thus approximating the phospholipids composition of mature lamellar bodies) at only 1% of their rate of hydrolysis of unsaturated molecules (Tables 1 and 2). This substrate preference corresponds to that shown by phospholipases from lysosomes.
Speculation: The substrate preferences of the lamellar body phospholipases may explain the ability of these enzymes to coexist with surfactant phospholipid in the mature organelle. In the developing lamellar body, phospholipase A2 may have a role to perform in the removal of unsaturated phosphatidylocholine molecules and their remodeling to the dipalmitoyl species.
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Health, M., Jacobson, W. THE NATURE OF THE PHOSPHOLIPASES A OF LUNG LAMELLAR BODIES. Pediatr Res 14, 846–847 (1980). https://doi.org/10.1203/00006450-198006000-00016
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DOI: https://doi.org/10.1203/00006450-198006000-00016