N-Linked Oligosaccharide Processing Enzymes as Molecular Targets for Drug Discovery

Abstract

α Glucosidases (EC 3.2.1.20) are also exo acting carbohydrases, catalyzing the release of α D glucopyranose from the non reducing ends of various substrates, 1,2) and on the basis of amino acid sequence similarities, α glucosidases are classified into two families, family 13 and family 31. 3,4) Endoplasmic reticulum (ER) glucosidases, glucosidase I (EC 3.2.1.106) and glucosidase II (EC 3.2.1.84), are key enzymes in the biosynthesis of asparagine linked oligosaccharides that catalyze the first processing event after the transfer of Glc3Man9GlcNAc2 to proteins. These enzymes are a target for inhibition by anti viral agents that interfere with the formation of essential glycoproteins required in viral assembly, secretion and infectivity.5) Many papers reported that inhibitors of α glucosidases are potential therapeutics for the treatment of such diseases as viral diseases, cancer and diabetes. 5,6) However, many screenings of α glucosidase inhibitors did not use enzymes from target tissues or organs. We think that the molecular recognitions of three kinds of glucosidases (family 13, family 31 α glucosidases and ER glucosidases) are different. Therefore, the glycon and aglycon specificity profiling of glucosidases has been an important approach for the research of glucosidase inhibitors.In this research, we first describe the glycon and aglycon specificity profiling of glucosidases using small molecules as probes. Next, compounds designed and synthesized as glucosidase inhibitor candidates were evaluated with regard to their ability to inhibit three kinds of glucosidases. Finally, the glucosidase inhibitor candidates were tested for their anti viral activities in a cell culture system.Glycon specificity profiling of glucosidases using chemically modified substrates. Chemically modified substrates are effective methods in the study of substrate specificity profiling. We have applied this approach to family 13 and family 31 α glucosidases, 7 10) ER glucosidases, 11,12) α galactosidases 8,13) and α mannosidases 8,14) using partially substituted monosaccharides. We used all of the monodeoxy analogs of p nitrophenyl α D glucopyranoside (PNP α Glc) 1 4 (Fig. 1) as chemically modified substrates for glycon specificity profiling. We investigated the hydrolytic activities of family 13 and family 31 α glucosidases and ER glucosidase II of PNP α Glc and its deoxy derivatives 1 4, and checked the inhibitory activities of ER glucosidase I of PNP α Glc and probes 1 4, so that PNP α Glc was not a substrate for ER glucosidase I. These results are shown in Table 1. 11,12) Clearly, of the four deoxy derivatives of PNP α Glc 1 4, family 31 α glucosidases and ER glucosidase II hydrolyzed the 2 deoxy glucopyranoside (1); its activity with 1 appeared to be substantially higher than that with PNP α Glc. Kinetic studies of the hydrolysis of PNP α Glc, 1 and 2 were also carried out (Table 2) Abstract: N-Linked oligosaccharide processing enzymes are key enzymes in the biosynthesis of N-linked oligosaccharides. These enzymes are a molecular t...

Design and Screening Strategies for α-Glucosidase Inhibitors Based on Enzymological Information

“…We have examined the substrate specificity ofglycosidases for inhibitor design using synthetic small molecules [12][13][14][15][16][17][18][19][20][21], some of which are summarized in Fig. (1).…”

Efficient protective activity of a planar catechin analogue against radiation-induced apoptosis in rat thymocytes

“…9 The planar catechin also shows several biological activities, such as remarkable a-glucosidase inhibition, and anti-virus and anti-tumour activities. 7d, 10 We report herein that the enhanced radioprotective activity of the planar catechin against X-ray induced apoptosis in rat thymocytes compared to that of (+)-catechin. The biological data using rat thymocytes together with chemical data, such as radical-scavenging rates of the catechins as well as their lipophilicity provide fundamental and valuable information to develop effective radioprotective agents without toxicity.…”

A Planar Catechin Analogue as a New Type of Synthetic Antioxidant

“…As a-glycosidase catalyzes theˆnal step in the digestive process of carbohydrates, the strong inhibitory eŠect on a-glycosidase suggested that PCA may be used as a lead compound for the development of antidiabetic therapeutics, similar to acarbose and voglibose which are known to reduce postprandial hyperglycemia primarily by interfering with carbohydrate digesting enzymes and delaying glucose absorption. Potent antiviral activity of PCA was also shown by signiˆcant inhibition of Newcastle Disease Virus infection of BHK cells (24). Considering the strong inhibitory eŠect on a-glucosidase, the antiviral activity of PCA may be attributed to inhibition of glucosidase during protein synthesis that is essential for virus proliferation (25).…”