Effect of Desulphated Heparin Oligosaccharides in Inhibiting Iduronate-2-sulphatase Activity

Introduction Mucopolysaccharidoses Type II (MPS II) is a rare inherited disease caused by mutation in IDS gene encoding iduronate-2-sulphatase (IDS), an important enzyme in the glycosaminoglycans degradation pathway of heparan sulphate and dermatan sulphate. Current treatments such as enzyme replacement therapy is not effective in reducing the central nervous system manifestation while finding the suitable donor quite challenging in bone marrow transplantation. The use of small molecules in assisting misfolding protein has been explored as an alternative approach for potential therapy in MPS II treatment. In this study, we performed the inhibition assay of desulphated heparin oligosaccharides (DSH) small molecules using recombinant human iduronate-2-sulphatase (rhIDS) to identify potential candidate as pharmacological chaperone for MPS II.

Material and Methods The small molecules of DSH (DSH004, DSH006, DSH008, DSH010 & DSH012) were used in this study. All of the DSH candidates were tested in the inhibition assay as described in product insert of recombinant human iduronate 2-sulphatase (rhIDS) (2) (Figure 1). All DSH candidates were also tested on ATCC cell for specificity testing.

Results The results of inhibition assay for DSH candidates were shown in table 1. ▪ Figure 2 illustrated the inhibition profiling of each small molecules of DSH. There were no significant different in the inhibition of IDS activity in ATCC cells (p>0.05).

Discussion and Conclusion Inhibition concentration (IC50) referring to concentration required to produce 50% inhibition of enzyme activity. A lower IC50 generally means a more potent inhibitor (3) while inhibition constant (Ki ) indicates the binding affinity of the inhibitors. It was observed that DSH004 shows the highest value of IC50 and Ki compared to other DSH candidates. Although DSH004 demonstrate the highest Ki value, high IC50 value may cause toxicity to the cells. Overall, among all DSH candidates, DSH006 shows a promising outcome in inhibiting the IDS activity and therefore may have the potential to be a suitable candidate as the pharmacological chaperone for MPS II.