Homonojirimycin and N-methyl-homonojirimycin inhibit N-Iinked oligosaccharide processing

Abstract

Homonojirimycin (HNJ) and N-methylhomonojirimycin (MHNJ) were tested as inhibitors of the purified glycoprotein processing enzymes, glucosidase I and glucosidase II. MHNJ was a reasonably good inhibitor of glucosidase I (Ki = 1 x 10(-6) M) and was about three times as effective on this enzyme as was HNJ. On the other hand, HNJ inhibited glucosidase II with a Ki of about 1 x 10(-6) M, whereas MHNJ was three times less effective (Ki = 3 x 10(-5) M). However, the butyl derivative of HNJ had very low activity toward these two processing glucosidases. HNJ and its methyl derivative were also tested in vivo using influenza virus-infected MDCK cells, and measuring the inhibition of N-linked oligosaccharide processing of the viral envelope glycoproteins. With 100 micrograms/ml of MHNJ in the medium, essentially all of the N-linked oligosaccharide chains of the virus were of the "high-mannose" type with the major structure being characterized as Glc3Man9(GlcNAc)2. Similar results were obtained with HNJ although this compound was less effective in vivo as well as in vitro. These results are in keeping with these inhibitors being effective at the glucosidase I step. Both inhibitors were also tested in MDCK cell cultures to determine whether they affected the in vivo synthesis of proteins, or of lipid-linked saccharides. In contrast to deoxynojirimycin, which has been reported to inhibit the formation of lipid-linked saccharides, no effects were seen on either the incorporation of mannose into lipid-linked saccharides or the incorporation of leucine into protein.

In vitro inhibition and intracellular enhancement of lysosomal α‐galactosidase A activity in Fabry lymphoblasts by 1‐deoxygalactonojirimycin and its derivatives

“…Intracellular enzyme activity in normal lymphoblasts was also decreased after cultivation with DNJ, α‐HNJ and castanospermine (CAS), which are ER‐processing α‐glucosidase inhibitors (data not shown). N‐Linked oligosaccharide chains of glycoproteins synthesized in the presence of DNJ or α‐HNJ have essentially been characterized as Glc 3 Man 9 GlcNAc 2 [29]. The inability of cells to remove d ‐glucose from N‐linked oligosaccharides can have profound effects on synthesis, transport and/or secretion of the given glycoproteins which interact with ER chaperones such as calnexin and calreticulin [9].…”

“…N‐Alkyl derivatives of DGJ. The N ‐alkyl derivatives of DGJ were studied for α‐Gal A inhibition because N ‐alkylation of DNJ and α‐HNJ resulted in analogs with increased potency and substrate specificity on digestive α‐glucosidases and processing α‐glucosidase I [26–29], and N ‐alkylation of DNJ and DGJ increased the inhibitory potential toward glucosyltransferase [30,31]. However, N ‐alkylation of DGJ markedly lowered its inhibitory activity toward α‐Gal A (Table 1).…”

Naturally Occurring Iminosugars and Related Alkaloids: Structure, Activity and Applications

“…-HNJ and its synthetic N-methyl derivative (N-methyl--HNJ) (10) were evaluated for the inhibition of N-linked oligosaccharide processing of the viral envelope glycoproteins using an influenza virus-infected Madin-Darby canine kidney (MDCK) cell [23]. By treatment with 100 g/ml of N-methyl--HNJ in the medium, essentially all of the N-linked oligosaccharide chains of the virus were of the high mannose type with the major structure being characterized as Glc 3 Man 9 GlcNAc 2 .…”

Piperidine homoazasugars: Natural occurrence, synthetic aspects and biological activity study

“…62,63 α-HNJ 3 and its N-methyl derivative 91 are more potent against α-glucosidase I both in vitro and in cell culture. 64 So it is expected that these homonojirimycins would show excellent anti-HIV activity. Surprisingly, both HNJ 3 and Me-HNJ 91 showed no significant anti-HIV activity even at concentrations of 500 µg/mL.…”