Affinity partition of proteins in aqueous two-phase systems containing polyoxyethylene glycol-bound ligand and charged dextrans.

The partition of the delta 5 leads to 4 3-oxosteroid isomerase of Pseudomonas testosteroni in aqueous two-phase systems containing both the macroligand, polyoxyethylene glycol-bound estradiol, and charged (cationic or anionic) dextrans has been studied. If the enzyme is well retained in the upper phase by an adequate amount of macroligand, it is possible to improve the removal of the contaminating proteins by extracting them into a lower phase containing positively or negatively charged dextran. Some mult-step extraction experiments were carried out to purify isomerase, by washing the upper phase successively with cationic and anionic dextran-rich phases.