Some studies on the metabolism of phospholipids in Golgi complex from bovine and rat liver in comparison to other subcellular fractions

Abstract

1. 1. Golgi complex, rough and smooth microsomes, plasma membranes, mitochondria, and nuclei from bovine liver were isolated and the purity assessed using specific marker enzymes.

2. 2. Cholinephosphotransferase and acyl-CoA:1,2-diacyl-sn-glycerol acyltransferases were found to be absent in the Golgi complex, mitochondria, plasma membrane, and nuclei. The de novo synthesis of lecithin and triacylglycerols is apparently localized exclusively in the smooth and rough endoplasmic reticulum.

3. 3. Acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase was found to be localized mainly in rough and smooth microsomes from bovine and rat liver; though also significant activity was found in the Golgi complex of bovine liver. On the other hand, no significant acylation of 1-acyl-sn-glycero-3-phosphorylcholine could be shown in the Golgi system from rat liver.

4. 4. Phosphatidylglycerol synthesis was found to take place predominantly in rat liver mitochondria. Significant synthesis of this phospholipid was, however, also found in rough and smooth microsomes and in Golgi of rat liver.

5. 5. The Golgi complex of rat liver was shown to contain both phospholipase A1 and A2 activities acting on exogenous phosphatidylethanolamine, the activity of the former being somewhat larger.