STUDY OF FUMARASE ACTIVITY IN NONCONVENTIONAL MEDIA .2.

The hydration of fumarate and the dehydration of L-malate catalysed by fumarase were investigated in water/methanol and water/formamide one phase systems. The effects of the amount of organic solvent on the max imum velocity (V-max), the Michaelis-Menten constant (K-M) and the equ ilibrium constant (K-eq) were studied for both the reaction media. The denaturing power of both methanol and formamide was observed together with the familiar decrease of the K-M. Fumarase catalysis in water/me thanol systems was further investigated by evaporating the organic sol vent and evaluating the degree of reversibility of the inactivation. R eversibility of formamide denaturation was also investigated. The effe cts of phosphate concentration in the reaction medium with different a mounts of methanol was investigated following the variation of the kin etic parameters of the hydration reaction. At high concentrations of p hosphate an inhibiting effect appeared. Time-dependent denaturation wa s also investigated and a remarkable instability of fumarase in system s with percentages (v/v) of formamide higher than 10% was observed. 10 % formamide proved to be less deactivating than the other non-conventi onal reaction media so far employed.