NONTHERMAL EFFECTS OF A CERAMICS RADIATION ON REVERSIBILITY OF LACTATE-DEHYDROGENASE REACTION

Non-thermal effects of a ceramics radiation on reversibility of lactat e dehydrogenase reaction have been investigated using the enzyme irrad iated on cooling, and a pyruvate/NADH (system I) or a lactate/NAD(+) ( system II) as substrate. The K-m for lactate in the system II using th e irradiated enzyme tended to decrease just like balancing with the in crease in K-m for pyruvate in system I, The V-max/K-m for system II wa s increased 2.3-fold by the 18-h irradiated enzyme, Each enthalpy and entropy change in system II using the 18-h irradiation of the enzyme w as decreased by 21 kJ mol(-1), although that in system I was increased by 12 kJ mol(-1), From a thermodynamic analysis, it was estimated tha t solvation of the active center of LDH was promoted and stabilized by the irradiation, and that it caused this regulation of the reversibil ity of LDH.