FIGURE 3.

Glycopeptide substrate specificity of ppGalNAc T isoforms. Shown is random (glyco)peptide substrate, GPIV (red, diamond), GPIV-C (purple, upward triangle), GPV (blue, square), and GPV-C (light blue, inverted triangle), glycosylated by ppGalNAc T1 (A panels), T2 (B panels), T14 (C panels), T3 (D panels), T6 (E panels), T5 (F panels), T13 (G panels), and T16 (H panels). Left panels represent mole fraction of [³H]GalNAc (50 μm) transferred onto (glyco)peptide substrate (1.5–1.7 mm) as a function of time as described under “Experimental Procedures.” Right-hand panels represent G10 gel filtration chromatograms of overnight incubations, demonstrating incorporation of [³H]GalNAc into (glyco)peptide substrate (fractions 27–33) with minimal hydrolysis (i.e. free GalNAc, fractions 37–43).