Figure 3.

Elution profile of DEAE-Toyopearl chromatography of PPD. Enzyme extracts were used after ammonium sulfate precipitation (30%–70% saturation). The column was equilibrated with 20 mm Tris-HCl buffer (pH 7.5) and eluted with the same buffer containing a linear gradient of NaCl (0–0.35 m) at a flow rate of 1 mL/min. Three-milliliter fractions were collected. The enzyme assay and conditions were as described in Figure 2. ⋄, Protein concentrations were estimated with A₂₈₀; •, PPD activity; —, NaCl concentration. The peak fractions were designated type 1 (front peak) and type 2 (back peak) by the order of elution.