title: The brush border of rabbit kidney, a cellular compartment free of glycolytic enzymes.
abstract: Activities of four enzymes of the glycolytic pathway, hexokinase, glyceraldehyde 3-phosphate dehydrogenase, pyruvate kinase and lactate dehydrogenase, were determined in a vesicular brush-border preparation from rabbit kidneys. The specific activities of the enzymes were decreased several-hundredfold in the brush-border preparation compared with a kidney homogenate, but the enzymes were not totally absent. Density-gradient centrifugation of the brush-border preparation yielded brush border of even higher purity and also a characteristic pattern of distribution for each of the contaminating intracellular membranes. The presence of hexokinase in the brush-border preparation could be traced to contaminating mitochondria, and that of glyceraldehyde 3-phosphate dehydrogenase, pyruvate kinase and lactate dehydrogenase to contaminating vesicles derived from the endoplasmic reticulum. The brush-border vesicles contained some ATP. An intravesicular concentration of 0.1mm was estimated, indicating that the vesicles had retained at least a part of their original content. Experiments in which fluorescein isothiocyanate-dextran (mol.wt. 20000) was present during cell lysis revealed that much, but not all, of the brush-border contents had been exchanged with the medium. The complete absence of glycolytic enzymes from brush-border vesicles, which had retained part of their original content, indicates that the brush border does not contain glycolytic enzymes in vivo and can be thought of as a compartment of its own, somehow separated from the cytoplasm.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000201:enzymology*; D002499:Centrifugation, Density Gradient; D005260:Female; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D006019:Glycolysis; D006593:Hexokinase / Q000378:metabolism; D066298:In Vitro Techniques; D007668:Kidney / Q000201:enzymology* / Q000648:ultrastructure; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D008871:Microvilli / Q000201:enzymology*; D011092:Polyethylene Glycols / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism; D011770:Pyruvate Kinase / Q000378:metabolism; D011817:Rabbits
chemical_list: D011506:Proteins; D011092:Polyethylene Glycols; D000255:Adenosine Triphosphate; D007770:L-Lactate Dehydrogenase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D006593:Hexokinase; D011770:Pyruvate Kinase