Inhibition of purified lysosomal phospholipase A1 by beta-adrenoceptor blockers

Anuradha S. Pappu, Paul J. Yazaki, Karl Y. Hostetler

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


Inhibition of rat liver lysosomal phospholipases is one of the main events that leads to accumulation of tissue phospholipids during drug-induced phospholipidosis. Drug inhibition of lysosomal phospholipase A may occur by direct effects of drugs on the enzyme (or substrate) or by drug-induced increases in intralysosomal pH. Although beta-adrenoceptor blockers have not been reported to cause lipid storage, they do inhibit lysosomal phospholipase A. To investigate the structural requirements for drug inhibition, we studied the effects of six beta-adrenoceptor blockers on purified rat liver lysosomal phospholipase A1. The agents studied include: propranolol, timolol, metoprolol, practolol, atenolol and the combined alpha and beta adrenoceptor blocking agent, labetalol. The drugs varied by two logs in their abilities to inhibit phospholipase A1 activity. The relative inhibitory potencies were propranolol > labetalol ≫ timolol > metoprolol ≫ practolol > atenolol. Our studies identify drug hydrophobicity as a key determinant for phospholipase A1 inhibition. A strong negative correlation was noted between the octano/water partition coefficients and IC50 for phospholipase inhibition (r = -0.91). The ability of propranolol to inhibit phospholipase A1 was identical for the d, l and the d and l stereoisomers.

Original languageEnglish (US)
Pages (from-to)521-524
Number of pages4
JournalBiochemical Pharmacology
Issue number4
StatePublished - Feb 15 1985
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Pharmacology


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