Introduction of oxygen into the alkyl chain of N-decyl-dNM decreases lipophilicity and results in increased retention of glucose residues on N-linked oligosaccharides

N-Alkylation of the -glucosidase inhibitor 1-deoxynojirimycin(dNM) dramatically increases its inhibitory potency (Tan etal., J. Biol. Chem., 266, 14504–14510, 1991). However,the possibility of extending the alkyl chain to N-decyl-dNMis limited by an increase of detergent-like (amphiphilic) propertiesof long-chain alkylated dNM derivatives. Substitution of methylenegroups in the N-decyl chain by oxygen reduced the amphiphilicityof N-decyl-dNM derivatives, while retaining their superior inhibitoryproperties. In intact HepG2 cells, the compound N-7-oxadecyl-dNMwas found to result in the most pronounced retention of glucoseresidues on N-linked glycans. Permeabilization of the plasmamembrane with the bacterial toxin Streptolysin O improves theinhibitory properties of the derivatives N-3,6,9-trioxadecyl-,N-7,10,13-trioxatetradecyl-, N-3-oxadecyl- and N-7-oxadecyl-dNM,but not those of dNM. These observations suggest differencesin the mode of entry of the oxygen-substituted dNM derivativesin comparison with dNM. We observed that the dNM derivativeN-3,6,9-trioxadecyl-dNM, devoid of inhibitory activity in intactcells, was inhibitory in Streptolysh O-permeabilized cells.Thus, the permeability barriers posed by plasma membrane andendoplasmic reticulum membrane are not equivalent. The use ofa permeabilized cell system thus allows the elaboration of inhibitoryprinciples for novel bioactive compounds where study of theisolated enzymes may not be possible, and where intact cellsare not a suitable target due to permeability barriers. -glucosidase inhibition N-linked glycosylation oxygen-substituted N-decyl-dNM derivatives permeabilized cells