Specifically increased solubility of enzymes in polyethyleneglycol solutions using polymer-bound triazine dyes

The enzymes glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and 3-phosphoglycerate kinase (EC 2.7.2.3), present in an extract of Bakers' yeast, are largely kept in solution by minor amounts of polyethylene glycol-bound triazine dyes (Procion yellow HE-3G and Procion olive MX-3G) even when the solution contains such concentrations of polyethylene glycol (12.5% w/w) which normally precipitate the enzymes. The specific prevention from precipitation can be used for purification of enzyme, preferentially in dealing with crude extracts, which has been demonstrated in this work. A 3.4-fold purification of glucose-6-phosphate dehydrogenase has been achieved with good recovery (93%). Further purification has been possible by combining the recovered (enzyme-containing) supernatant liquid with a solution of dextran which generates an aqueous two-phase system. The lower, dextran-containing phase extracts part of the remaining bulk proteins leaving the target enzyme in the upper phase. The advantages of this method for enzyme purification in large scale are discussed.