FIGURE 2.

GlcNAc-1-phosphotransferase activity toward various acceptors. Cathepsin D (▴), NPC2 (■), RNase B (×), and soybean agglutinin (♦) were compared as acceptors for α₂β₂γ₂ (A) and α₂β₂ forms (B) of GlcNAc-1-phosphotransferase. Various concentrations of the substrates and either 1.2 μg of the α₂β₂γ₂ or 0.97 μg of the α₂β₂ GlcNAc-1-phosphotransferase were incubated in 50 mm Tris-HCl, pH 7.4, 10 mm MgCl₂, 10 mm MnCl₂, 75 μm UDP-[³H]GlcNAc (1 μCi), 2 mg/ml bovine serum albumin in a final volume of 50 μl for 1 h at 37 °C. The incorporated [³H]GlcNAc-P was determined by scintillation counting. The activity of the GlcNAc-1-phosphotransferase was expressed as moles of [³H]GlcNAc-P transferred per h/mol of the GlcNAc-1-phosphotransferase.