Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.5 (5'-nucleotidase)
 3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We report the total lipid composition and phospholipid asymmetry of a plasma membrane preparation isolated from a Schwann cell line (NF1T) derived from a human neurofibroma. The specific activities of three plasma membrane markers (5'-nucleotidase, Na-K-ATPase, and CNPase) were 8-fold, 12-fold, and 16-fold higher, respectively, in the plasma membrane fraction compared to the specific activities found in the total homogenate. The specific activities of the marker enzymes of intracellular membranes in the isolated plasma membrane fraction indicated little contamination with intracellular organelles. The enrichment of cholesterol (3-fold), sphingomyelin (3-fold), and glycolipids (cerebrosides 8-fold, sulfatides 5-fold) also indicated a high degree of purity of the plasma membrane fraction. The high content of phosphatidylinositol and phosphatidylcholine (10% and 44% of total phospholipid) and the low phosphatidylserine and phosphatidylethanolamine content (3% and 14% of the total phospholipid) were also characteristic of the plasma membrane fraction derived from this cell line. The transbilayer phospholipid distribution of the plasma membrane in intact cells and in the isolated plasma membrane fraction was investigated by using phospholipase A2 (bee venom) and sphingomyelinase (S. aureus). The phospholipid asymmetry of NF1T plasma membrane followed the general features of phospholipid asymmetry in eukaryotic cells: sphingomyelin and phosphatidylcholine were preferentially located in the outer leaflet (90% and 89%, respectively) while the aminophospholipids phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol were in the inner half of the membrane (85%, 96%, and 69%, respectively). A high percentage of the total plasma membrane phosphatidylinositol (31%) was found in the outer side of the membrane indicating a decreased asymmetric distribution for this negatively charged phospholipid. The phospholipid asymmetry found in the plasma membrane vesicle fraction corroborated the phospholipid asymmetry of the intact cells, thus confirming that the plasma membrane vesicles maintained the original orientation and lipid asymmetry after homogenization and/or sonication.
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PMID:Lipid composition and phospholipid asymmetry of membranes from a Schwann cell line. 926 Jul 48

Axolemmal fractions are isolated by discontinuous gradient centrifugation of purified myelinated axons which have been osmotically shocked to yield axons, myelin and axolemma. The axolemmal fractions are enriched in surface membrane marker enzymes such as Na(+),K(+)-activated ATPase, 5'-nucleotidase and acetylcholinesterase. Mixing experiments with labeled microsomes and mitochondria show that these contaminants are effectively screened out by the preparation procedure. The fractions contain significant amounts of 2',3'-cyclic nucleotide-3'-phosphohydrolase and are enriched in higher molecular weight proteins. These membrane preparations may be useful in analytical studies of mammalian axolemmal composition.
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PMID:Isolation of axolemma-enriched fractions from bovine central nervous system. 1960 72


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