SEVERAL MECHANISMS HAVE BEEN SUGGESTED TO EXPLAIN HOW SECRETORY CELLS REMOVE FROM THE PLASMALEMMA THE EXCESS MEMBRANE RESULTING FROM THE INSERTION OF GRANULE MEMBRANE DURING EXOCYTOSIS: intact patches of membrane may be internalized and then reutilized within the cell; alternatively these membranes may be either disassembled to subunits or degraded. In the latter case new membranes should be sy...

Experiments were performed to localize the hepatic microsomal enzymes of phosphatidylcholine, phosphatidylethanolamine, and triacylglycerol biosynthesis to the cytoplasmic or lumenal surface of microsomal vesicles. Greater than 90 percent of the activities of fatty acid-CoA ligase (EC 6.2.1.3), sn-glycerol 3-phosphate acyltransferase (EC 2.3.1.15), lysophosphatidic acid acyltransferase, diacylg...

A pigeon pancreas microsomal system supplemented with microsomal supernatant fluid or pH 5 enzyme incorporates radioactive amino acids into purified amylase. Several parameters of the incorporation system are presented. TrypCc digestion of the isolated radioactive amylase shows that the amino acids are incorporated into peptide linkage within the protein, as in amylase synthesized in viva. The ...

The influence of membrane cholesterol content on 3-hydroxy-3-methylglutaryl CoA reductase (HMG-CoA reductase, EC 1.1.1.34) in rat liver microsomes was investigated. Microsomes were enriched in cholesterol by incubation with egg phosphatidylcholine-cholesterol vesicles and the nonspecific lipid transfer protein from rat liver. By this method, the microsomal cholesterol content was 2.5-fold enhan...

A pigeon pancreas microsomal system supplemented with microsomal supernatant fluid or pH 5 enzyme incorporates radioactive amino acids into purified amylase. Several parameters of the incorporation system are presented. TrypCc digestion of the isolated radioactive amylase shows that the amino acids are incorporated into peptide linkage within the protein, as in amylase synthesized in viva. The ...

ATPase activity and Ca2+ uptake were examined in microsomal membrane fractions isolated from guinea pig stomach smooth muscle which had been exposed to phospholipase C (PLC). Basal Mg2+-ATPase, Na+, K+-ATPase and Ca2+, Mg2+-ATP activities were inhibited in a time dependent manner by PLC treatment. There was positive correlations between each of these ATPase activities and total phospholipid con...