Purified recombinant PPT1 derived from stable overexpression in CHO cells. A, Mono S chromatography of conditioned medium. Solid line, UV absorption profile; closed circles, PPT1 enzyme activity expressed in arbitrary fluorescence units; dotted line, gradient elution profile (NaCl concentration increased from 25 mM to 350 mM NaCl). B, Fractions from gradient elution. Highly purified PPT1 (migrating as a 34 kDa band) is eluted. P, post-dialysis conditioned medium; L, material loaded onto the column.