Journal of Lipid Research, Vol. 7, 612-620, September 1966
Copyright © 1966 by Lipid Research, Inc.

Phospholipase activity in rat liver mitochondria studied by the use of endogenous substrates

Pål Bjørnstad

Institute of Clinical Biochemistry, University of Oslo, Rikshospitalet, Oslo, Norway

The hydrolysis of endogenous phosphatidyl ethanolamine and lecithin in rat liver mitochondria has been studied by using mitochondria from rats injected with ethanolamine-1,2-¹⁴C or choline-1,2-¹⁴C. A phospholipase A-like enzyme has been demonstrated, which catalyzes the hydrolysis of one fatty acid ester linkage in phosphatidyl ethanolamine and lecithin. Phosphatidyl ethanolamine is hydrolyzed in preference to lecithin and the main reaction products are free fatty acids and lysophosphatidyl ethanolamine. The further breakdown of lysophospholipids appears to be limited in mitochondria, which indicates that lysophospholipase activity is mainly located extramitochondrially. The enzymic system is greatly stimulated by calcium ions, and also slightly by magnesium ions, while EDTA inhibits it almost completely. These findings are discussed in relation to previous observations on the effect of calcium and of EDTA on the functions of mitochondria.

The possible function of the mitochondrial phospholipase for the formation of phospholipids with special fatty acids at the - and -position is discussed.

Supplementary key words rat • liver • mitochondria • enzyme • phospholipids • hydrolysis • calcium ions • inactivation

Submitted on February 21, 1966
Accepted on May 10, 1966

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?