Bryan Winchester

Synthesis from D-mannose of 1,4-dideoxy-1,4-imino-L-ribitol and of the α-mannosidase inhibitor 1,4-dideoxy-1,4-imino-D-talitol

Abstract The syntheses of 1,4-dideoxy-l,4-imino-L-ribitol and of 1,4-dideoxy-l,4-imino-D-talitol from D-mannose are described. 1,4-Dideoxy-l,4-imino-D-talitol is a specific and competitive inhibitor of human liver α-mannosidase in vitro and also blocks the lysosomal catabolism of asparigine-linked glycans of glycoproteins in vivo .

Castanospermine-Induced Deficiency of Lysosomal β-D-Glucosidase: A Model of Gaucher’s Disease in Fibroblasts

Many naturally occurring or synthetic polyhydroxylated indolizidine, piperidine and pyrrolidine alkaloids are specific potent inhibitors of mammalian glycosidases [1,2]. Some of these compounds are also lysosomotropic because of their weakly basic nature and can be used to induce a reversible deficiency of a lysosomal glycosidase in vivo or in cells in culture [3]. This can produce a phenocopy of the lysosomal storage disease that results from the genetic deficiency of the same enzyme. Such model systems can be used to study the dynamics of accumulation of storage products and their dispersal on restoration of the activity on withdrawal of the inhibitor, and to identify reversible and irreversible steps in pathogenetic mechanisms.

Forms and intracellular distribution of α-d-mannosidases in murine liver and spleen

Abstract 1. 1. The intracellular distribution of α- d -mannosidase in homogenates of murine liver and spleen was investigated by differential and gradient density centrifugation. 2. 2. In both tissues an enzyme with a neutral pH optimum was found in the cytosol together with an α- d -mannosidase with optimal activity between pH 5.5 and 6.0 which was also partially membrane-bound. 3. 3. In liver the acidic α- d -mannosidase was obtained almost entirely in a particulate form distributed equally between a heterogeneous low density region and heavy density lysosomes. 4. 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. 5. Antibody raised against the purified liver α- d -mannosidase immunoprecipitated a polypeptide from spleen which had the same molecular size. This acidic enzyme was the predominant type of α- d -mannosidase in spleen, but in contrast to liver, it was obtained mainly in a cytosoluble form, the remaining activity being present in the heterogenous light density compartment. 6. 6. Although both tissues contain the same molecular form of the acidic α- d -mannosidase, in murine spleen this enzyme does not appear to be associated with stable heavy density lysosomes.

The Molecular Basis of Canine Fucosidosis

Fucosidosis is the lysosomal storage disease resulting from a deficiency of α-L-fucosidase [EC3.2.1.51]. It has been described in children [1] and in pedigree English springer spaniels in Australia [2] and the United Kingdom [3]. Canine fucosidosis is a progressive neurological disorder with the onset of clinical signs occurring at 18-36 months, suggesting a similarity with the adult form (Type 2) of human fucosidosis. There is a vacuolation of neurones and glial cells throughout the dog brain and vacuolation is also present in epithelial cells of bronchi, bile duct tubules and lymphocytes. The disease is characterised biochemically by a deficiency of α-L-fucosidase in all cells and tissues and by the accumulation in tissues and excretion in urine of fucose-containing glycoasparagines [4]. Information concerning the mode of inheritance and molecular basis of the enzymic defect in canine fucosidosis is presented in this paper.