Study of fumarase activity in non-conventional media. Part I

Fumarase catalysed hydration of fumarate was investigated in water/organic solvent one-phase systems. The organic solvents used were ethylene glycol, glycerol and dimethylformamide. The effects of the amount of organic solvent on the maximum velocity (V_max), the Michaelis-Menten constant (K_M) and the equilibrium constant (K_eq) were studied in all the reaction media. Together with a denaturing power of the solvent evidenced by a systematic decrease of V_max also a surprising decrease of the K_M was registered as the percentage of organic solvent in the reaction media was increased. While the equilibrium constant of the reaction (K_eq = l-malate]/fumarate]) decreased when the percentage of organic solvent was raised. An interpretation of these facts was given. Time-dependent denaturation was also investigated and glycerol resulted the less denaturing of the solvents used, while the aprotic DMF exhibited the highest deactivation.