Enzyme activation and inactivation induced by low doses of irradiation

Activation phenomenon has been observed with two sets of enzymes under the conditions of low dosage irradiation. Activation was registered for angiote nsin-converting enzyme under in vitro gamma-irradiation (0.662 MeV, pulse d uration approx 10 s) at dose levels of 1-3 Gy and under X-ray irradiation ( approx 9 keV, pulse duration approx 10(-9)s) at dose levels of 2x10(-5) Gy. An activation effect has also occurred for native and recombinant horserad ish peroxidase and tobacco peroxidase under gamma-irradiation. The phenomen on observed is rationalized in terms of a kinetic model suggesting the exis tence of at least one activated-enzyme conformation induced by radiolysis. The activity oscillations registered in dense plasma focus experiments were rationalized using the same model with the corresponding kinetic equation converted into the form describing the decaying oscillations caused by exci ting force. The model analysis is presented.