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 alpha-glucosidase inhibitor 1-deoxynojiri-mycin (d NM) dramatically increases its inhibitory potency (Tan et al., J. Biol . Chem., 266, 14504-14510, 1991). However, the possibility of extendin g the alkyl chain to N-decyl-dNM is limited by an increase of detergen t-like (amphiphilic) properties of long-chain alkylated dNM derivative s. Substitution of methylene groups in the N-decyl chain by oxygen red uced the amphiphilicity of N-decyl-dNM derivatives, while retaining th eir superior inhibitory properties. In intact HepG2 cells, the compoun d N-7-oxadecyl dNM was found to result in the most pronounced retentio n of glucose residues on N-linked glycans. Permeabilization of the pla sma membrane with the bacterial toxin Streptolysin O improves the inhi bitory properties of the derivatives N-3,6,9-trioxadecyl-, N-7,10,13-t rioxatetradecyl-, N-3-oxadecyl- and N-7-oxadecyl-dNM, but not those of dNM. These observations suggest differences in the mode of entry of t he oxygen-substituted dNM derivatives in comparison with dMM. We obser ved that the dNM derivative N-3,6,9-trioxadecyl-dNM, devoid of inhibit ory activity in intact cells, was inhibitory in Streptolysin O-permeab ilized cells. Thus, the permeability barriers posed by plasma membrane and endoplasmic reticulum membrane are not equivalent. The use of a p ermeabilized cell system thus allows the elaboration of inhibitory pri nciples for novel bioactive compounds where study of the isolated enzy mes may not be possible, and where intact cells are not a suitable tar get due to permeability barriers.