Kinetic behavior of phosphotriesterase and its non-covalent complexes with polyelectrolyte in systems with polar and non-polar organic solvents

Soluble phosphotriesterase from E. coli DH5 alpha together with E. coli DH5 alpha cells with the phosphotriesterase activity were co-immobilized into poly(vinyl alcohol) (PVA) cryogel and studied in water/organic systems with polar and non-polar organic solvents. The phosphotriesterase activity was competitively inhibited by polar organic solvents. The inhibition constant correlated with the dielectric constant (epsilon) of the solvent. The rate of the enzyme-catalyzed reaction in biphasic non-polar solvent/water systems was independent of water/organic ratio and the hydrophobicity of the solvent. Formation of the non-covalent complexes with polyelectrolytes was suggested to enhance the resistance of the phosphotriesterase towards inactivation by organic solvents in their homogeneous mixtures with water.