title: The lactose synthetase particles of lactating bovine mammary gland. Characteristics of the particles.
abstract: 1. The conditions that promoted the solubilization of particulate lactose synthetase were effective for solubilizing the thiamine pyrophosphatase of the Golgi apparatus but differed from those effective for beta-glucuronidase or acid phosphatase of lysosomes. 2. Lactose synthetase-containing particles did not bind Mg(2+) or Cs(+) ions, suggesting that they are not related to endoplasmic reticulum membranes. 3. Intact lactose synthetase and thiamine pyrophosphatase particles banded isopycnically at a density of 1.143 in a sucrose gradient. The dissociated ;A' sub-unit of lactose synthetase, UDP-galactose hydrolase, p-nitrophenyl phosphate acid phosphatase, alkaline phosphatase and phosphodiesterase I were associated with particles of a broad density range from 1.12 to 1.20. Lysosomal enzymes beta-glucuronidase, arylsulphatase and beta-glycerophosphate acid phosphatase were associated with particles of density 1.20, 1.175 and 1.15 respectively. 4. Rate-zonal sedimentation studies indicated that lactose synthetase particles have S(20,w) values exceeding 24000s, corresponding to spherical particles of diameter exceeding 5.4x10(-5)cm. 5. Electron micrographs of lactose synthetase particles purified over 20-fold revealed small spherical bodies (0.1-0.5mu) resembling lysosomes, the smaller of which were attached to membranes, and larger heterogeneous spherical or oval bodies (0.7-1.8mu) resembling lipofuscin secretory granules. 6. The relationship between lactose synthetase particles and the Golgi origin of secretion granules is discussed.
mesh_terms: D000135:Acid Phosphatase / Q000032:analysis; D000469:Alkaline Phosphatase / Q000032:analysis; D000818:Animals; D002417:Cattle; D002499:Centrifugation, Density Gradient; D002501:Centrifugation, Zonal; D002586:Cesium; D005260:Female; D005964:Glucosyltransferases / Q000378:metabolism*; D005966:Glucuronidase / Q000032:analysis; D006056:Golgi Apparatus; D066298:In Vitro Techniques; D007774:Lactation; D008025:Ligases / Q000032:analysis*; D008247:Lysosomes; D008274:Magnesium; D008321:Mammary Glands, Animal / Q000201:enzymology*; D008854:Microscopy, Electron; D010744:Phosphoric Monoester Hydrolases / Q000032:analysis; D011247:Pregnancy; D012995:Solubility; D013429:Sulfatases
chemical_list: D002586:Cesium; D005964:Glucosyltransferases; D000469:Alkaline Phosphatase; D000135:Acid Phosphatase; D010744:Phosphoric Monoester Hydrolases; D013429:Sulfatases; D005966:Glucuronidase; D008025:Ligases; D008274:Magnesium