Trisaccharide Sulfate and Its Sulfonamide as an Effective Substrate and Inhibitor of Human Endo-<i>O</i>-sulfatase-1

Abstract

Human endo-<i>O</i>-sulfatases (Sulf-1 and Sulf-2) are extracellular heparan sulfate proteoglycan (HSPG)-specific 6-<i>O</i>-endosulfatases, which regulate a multitude of cell-signaling events through heparan sulfate (HS)-protein interactions and are associated with the onset of osteoarthritis. These endo-<i>O</i>-sulfatases are transported onto the cell surface to liberate the 6-sulfate groups from the internal d-glucosamine residues in the highly sulfated subdomains of HSPGs. In this study, a variety of HS oligosaccharides with different chain lengths and <i>N</i>- and <i>O</i>-sulfation patterns via chemical synthesis were systematically studied about the substrate specificity of human Sulf-1 employing the fluorogenic substrate 4-methylumbelliferyl sulfate (4-MUS) in a competition assay. The trisaccharide sulfate IdoA2S-GlcNS6S-IdoA2S was found to be the minimal-size substrate for Sulf-1, and substitution of the sulfate group at the 6-<i>O</i> position of the d-glucosamine unit with the sulfonamide motif effectively inhibited the Sulf-1 activity with IC₅₀ = 0.53 μM, <i>K</i>_i = 0.36 μM, and <i>K</i>_D = 12 nM.