Fig. 4.

Molecular basis of HE substrate specificity. (A) Enzymatic activity of BToV and PToV HE and their derivatives toward O-acetylated Sias of bovine submaxillary mucin (BSM) as determined by GC-MS. The extent of enzymatic de-O-acetylation (expressed in percentages on the y axis) was calculated by integrating mass-chromatogram surfaces of peaks corresponding to Neu5,9Ac₂ and Neu5,7,9Ac₃ in BSM samples that had been either mock treated or HE treated for different amounts of time (x axis). Open squares, Neu5,9Ac₂; closed circles, Neu5,7,9Ac₃. (B) Esterase activity toward the synthetic substrate pNPA.