Forms and intracellular distribution of alpha-D-mannosidases in murine liver and spleen.
1. The intracellular distribution of alpha-D-mannosidase in homogenates of murine liver and spleen was investigated by differential and gradient density centrifugation. 2. In both tissues an enzyme with a neutral pH optimum was found in the cytosol together with an alpha-D-mannosidase with optimal activity between pH 5.5 and 6.0 which was also partially membrane-bound. 3. In liver the acidic alpha-D-mannosidase was obtained almost entirely in a particulate form distributed equally between a heterogeneous low density region and heavy density lysosomes. 4. The lysosomal form of the liver enzyme was purified to electrophoretic homogeneity and shown to be a glycoprotein composed of four identical subunits of molecular weight 65 kDa. 5. Antibody raised against the purified liver alpha-D-mannosidase immunoprecipitated a polypeptide from spleen which had the same molecular size. This acidic enzyme was the predominant type of alpha-D-mannosidase in spleen, but in contrast to liver, it was obtained mainly in a cytosoluble form, the remaining activity being present in the heterogeneous light density compartment. 6. Although both tissues contain the same molecular form of the acidic alpha-D-mannosidase, in murine spleen this enzyme does not appear to be associated with stable heavy density lysosomes.
Abraham
D
D
Kennedy Institute of Rheumatology, London, England.
Bou-Gharios
G
G
Olsen
I
I
Shelton
I
I
Smith
R
R
Winchester
B
B
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000201:enzymology* / Q000648:ultrastructure; D008247:Lysosomes / Q000201:enzymology; D008361:Mannosidases / Q000378:metabolism*; D051379:Mice; D008854:Microscopy, Electron; D008970:Molecular Weight; D013154:Spleen / Q000201:enzymology* / Q000648:ultrastructure; D043323:alpha-Mannosidase
D008361:Mannosidases; D043323:alpha-Mannosidase