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Keywords:

  • chromogenic sugar sulfate;
  • glycosidases;
  • hexosaminidases;
  • substrates;
  • sulfatases

Abstract

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Systematic sulfation: Sulfated glycoconjugates are degraded either by desulfation followed by glycoside cleavage, or by glycoside cleavage followed by desulfation. To study these processes, here we report the synthesis of four regioisomerically sulfated p-nitrophenyl glucosaminides from the common precursor p-nitrophenyl N-acetyl-β-D-glucosaminide. These substrates allowed the rapid analysis of the substrate preferences of a set of four sulfatases and 24 hexosaminidases.

Sulfated carbohydrates are components of many glycoconjugates, and are degraded by two major processes: cleavage of the sulfate ester by a sulfatase, or en bloc removal of a sulfated monosaccharide by a glycoside hydrolase. However, these processes have proved difficult to study owing to a lack of homogeneous, defined substrates. We describe here the synthesis of a series of p-nitrophenyl β-D-glucosaminides bearing sulfate esters at the 2-, 3-, 4- or 6-positions, by divergent routes starting with p-nitrophenyl 2-acetamido-2-deoxy-β-D-glucopyranoside. The sulfated p-nitrophenyl β-D-glucosaminides were used to study the substrate specificity of four sulfatases (from Helix pomatia, Patella vulgata, abalone, and Pseudomonas aeruginosa), and revealed significant differences in the preference of each of these enzymes for desulfation at different positions around the sugar ring. The 3-, 4- and 6-sulfated p-nitrophenyl 2-acetamido-2-deoxy-β-D-glucosaminides were screened against a panel of 24 fungal β-N-acetylhexosaminidases to assess their substrate specificity. While the 4- and 6-sulfates were substrates for many of the fungal enzymes investigated, only a single β-N-acetylhexosaminidase, that from Penicillium chrysogenum, could hydrolyze the 3-sulfated p-nitrophenyl glycoside. Together these results demonstrate the utility of sulfated p-nitrophenyl β-D-glucosaminides for the study of both sulfatases and glycoside hydrolases.