A Nonionic Inhibitor with High Specificity for the UDP-Gal Donor Binding Site of Human Blood Group B Galactosyltransferase: Design, Synthesis, and Characterization

Abstract

9-(5-O-α-D-galactopyranosyl)-D-arabinityl-1,3,7-trihydropurine-2,6,8-trione (1) was designed and synthesized as a nonionic inhibitor for the donor binding site of human blood group B galactosyltransferase (GTB). Enzymatic characterization showed 1 to be extremely specific, as the highly homologous human N-acetylgalactosaminyltransferase (GTA) is not inhibited. The binding epitope of 1 demonstrates a high involvement of the arabinityl linker, whereas the galactose residue is only making contact to the protein via its C-2 site, which is very important for the discrimination between galactose and N-acetylgalactosamine, the substrate transferred by GTA. The approach can generate highly specific glycosyltransferase inhibitors.

Fragment Growing to Design Optimized Inhibitors for Human Blood Group B Galactosyltransferase (GTB)

“…This is time and resource intensive. [12] For the enzymatic reaction of GTB, the transfer of galactose from the donor substrate UDP-Gal onto an acceptor substrate results in the formation of UDP.B ecause UDP is an inhibitor of GTB, it must be re- . Our research group has shown that NMR spectroscopy is ap owerful tool for progress curve analysis; [25] we werea ble to determine inhibition constants for inhibitors of GTB from such experimentsb efore.…”

“…Our research group has shown that NMR spectroscopy is ap owerful tool for progress curve analysis; [25] we werea ble to determine inhibition constants for inhibitors of GTB from such experimentsb efore. This has previously been achieved by the use of alkaline phosphataseb yS chaefer et al [12] In contrast to the work by Schaefer et al,w ep erformed our inhibition studies at as lightly more acidic pD value of 5.8 in order to increase the solubility of the examined ligands and therefore substituted alkaline with acidic phosphatase from wheat germ. For the orientation of the core fragment (as shown in panel A), all three ligands show an identical binding mode.…”

“…[6,7] For pancreatic cancer, individuals of phenotype Bh ave a1 .5-fold higher incidence rate than individuals of phenotype O. [12] However,s uch substrate analogues have limited potentiald ue to their non-drug-like properties such as their typically high polarity. [9] Similarly,f or hepatocellular carcinomai th as been demonstrated that individuals of phenotype Bh ave am edian overall survival of only 34 months compared with 55 months for individuals of phenotype O.…”

“…[11] One example of such as ubstrate analogue for the inhibitiono fG TB from our group is shown in Figure 2. [12] However,s uch substrate analogues have limited potentiald ue to their non-drug-like properties such as their typically high polarity. [11] For GTB, af ragment screening revealed compound 1 (Figure2), which is the starting point for the work described herein.…”

Synthesis and biological evaluation of nonionic substrate mimics of UDP-Galp as candidate inhibitors of UDP galactopyranose mutase (UGM)

“…Schaefer et al 9,10 proposed that the ionic pyrophosphate group could be replaced by a nonionic group to increase bioavailability and facilitate penetration of cells and cell compartments to reach the target enzymes. This concept was first advanced to derive nonionic mimics of the sugar-nucleoside donor of the human blood group B galactosyltransferase.…”