Key result
A specific phospholipase assay for mouse endothelial lipase was developed, revealing that murine pre-heparin plasma lacks measurable EL activity, suggesting in vivo hydrolysis occurs on the cell surface.
A novel specific phospholipase assay for endothelial lipase was developed, demonstrating that EL hydrolysis of HDL phospholipids likely occurs on the cell surface rather than in circulating pre-heparin plasma.
Assay development warrants no change in clinical HDL assessment; leaves open cell-surface EL targeting for human studies.
Endothelial lipase (EL) is a major negative regulator of plasma HDL levels in mice, rabbits, and most probably, humans. Although this regulatory function is critically dependent on EL's hydrolysis of HDL phospholipids, as yet there is no phospholipase assay specific for EL in plasma. We developed such an assay for the mouse enzyme using a commercially available phospholipid-like fluorescent substrate in combination with an EL neutralizing antibody. The specificity of the assay was established using EL knockout mice and its utility demonstrated by detection of an increase in plasma EL phospholipase activity following exposure of wild-type mice to lipopolysaccharide. The assay revealed that murine pre-heparin plasma does not contain measurable EL activity, indicating that the hydrolysis of HDL phospholipids by EL in vivo likely occurs on the cell surface.
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Basu et al. (2012) studied Endothelial lipase activity assay development. Phospholipase assay specific for endothelial lipase was evaluated on Detection of EL phospholipase activity. A specific phospholipase assay for mouse endothelial lipase was developed, revealing that murine pre-heparin plasma lacks measurable EL activity, suggesting in vivo hydrolysis occurs on the cell surface.
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