| Abstract: | Affinity partitioning in aqueous two-phase systems composed of dextran and polyethylene glycol the latter being partially replaced by dye-substituted polymer was evaluated for the study of enzyme-dye interaction. The method was found excellently suited for the recognition of any interaction between a certain enzyme and triazine dyes by determining the actual partition coefficient, K. Two enzymes, intestinal alkaline phosphatase and yeast phosphofructokinase, were studied. Alkaline phosphatase binds more or less specifically to various triazine dyes. A number of substrates but also inorganic phosphate, NAD+ and selected chromophores are competing agents in enzyme-dye interaction whereas hydrophobic and uncompetitive inhibitors fail to compete with the dye. Thus, information on the chemical nature of the dye-enzyme interaction was obtained. Affinity partitioning turned out also appropriate to study the structural dynamics of enzymes. This was exemplified on the specific interaction of phosphofructokinase with a number of triazine dyes. A change of the allosteric properties of the enzyme in respect to ATP-inhibition and its reversibility was indicated by a corresponding alteration of the partition coefficient. The results are discussed in terms of a conformational change of the enzyme. |
