Quail Sulf1 function requires asparagine-linked glycosylation.

The heparan sulfate endosulfatases Sulf1 and Sulf2 are cell-surface enzymes that control growth factor signaling through regulation of the 6-O-sulfation states of cell-surface and matrix heparan sulfate proteoglycans. Here, we report that quail Sulf1 (QSulf1) is an asparagine-linked glycosylated protein. Domain mapping studies in combination with a protein glycosylation prediction program identified multiple asparagine-linked glycosylation sites in the enzymatic and C-terminal domains. Glycosylation inhibitor studies revealed that glycosylation of QSulf1 is essential for its enzymatic activity, membrane targeting, and secretion. Furthermore, N-glycanase cleavage of asparagine-linked sites in native QSulf1 provided direct evidence that these N-linked glycosylation sites are specifically required for QSulf1 heparin binding and its 6-O-desulfation activity, revealing that N-linked glycosylation has a key role in the control of sulfatase enzymatic function.