title: Biosynthesis of liver membranes. Incorporation of ( 3 H)leucine into proteins and of ( 14 C)glucosamine into proteins and lipids of liver microsomal and plasma-membrane fractions.
abstract: 1. The smooth-and rough-microsomal and the light and heavy plasma-membrane fractions of mouse liver homogenates were prepared and characterized by using biochemical markers. 2. The hexosamine/protein ratio was threefold higher in the plasma membranes than in the smooth-microsomal fraction. Glucosamine was bound only to protein, and galactosamine was attached mainly to lipids. 3. [(3)H]-Leucine and [(14)C]glucosamine were injected into animals and the rates of incorporation of radioactivity into the fractions were determined. Both precursors were rapidly incorporated into the microsomal fractions, but plasma membranes showed a slower rate of synthesis which reached a maximum at 2-4h after intravenous administration. 4. The light- and heavy-plasma-membrane fractions showed similar patterns of incorporation, and therefore a precursor-product relationship appears unlikely. 5. Plasma membranes, especially the light subfraction, showed appreciable incorporation of hexosamine into chloroform-methanol-soluble components which were shown to be mainly glycolipids. 6. The results indicate that liver plasma-membrane proteins and glycoproteins are synthesized at similar rates. However, glycolipid synthesis in plasma membranes occurred more rapidly.
mesh_terms: D000818:Animals; D002247:Carbon Isotopes; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism*; D002501:Centrifugation, Zonal; D002725:Chloroform; D005688:Galactosamine / Q000378:metabolism; D005944:Glucosamine / Q000378:metabolism*; D006017:Glycolipids / Q000096:biosynthesis; D006023:Glycoproteins / Q000096:biosynthesis; D006595:Hexosamines / Q000378:metabolism; D007275:Injections, Intravenous; D007930:Leucine / Q000378:metabolism*; D008055:Lipids / Q000096:biosynthesis*; D008099:Liver / Q000378:metabolism*; D000432:Methanol; D051379:Mice; D008862:Microsomes, Liver / Q000378:metabolism*; D014176:Protein Biosynthesis; D012995:Solubility; D014316:Tritium
chemical_list: D002247:Carbon Isotopes; D006017:Glycolipids; D006023:Glycoproteins; D006595:Hexosamines; D008055:Lipids; D014316:Tritium; D005688:Galactosamine; D002725:Chloroform; D007930:Leucine; D005944:Glucosamine; D000432:Methanol