Photodynamically induced changes of acetylcholinesterase activity from human erythrocytes

The light and photodynamic actions on acetylcholinesterase activity from hu man erythrocytes were studied. After light irradiation (670 nm, semiconduct ing low power laser) the maximum reaction rate increased from 13.3 to 14.8 mu mol per ml packed cells per min for an energy dose 9 J, and above that d ose it decreased (10.8 mu mol per ml packed cells per min for an energy dos e of 15 J). The Michaelis-Menten constant changed in the opposite direction . After irradiation of erythrocyte suspension in the presence of zinc phtha locyanine the reaction rate increased, reaching the maximum for energy dose of 0.75 J (16.85 in comparison to the control value of 14.7 mu mol per ml packed cells per min. Similarly, the Michaelis-Menten constant decreased re aching a minimum for an energy dose of 0.75 J (0.04 mM compared to 0.07 mM for control). incubation of erythrocytes with the dye in the dark increased the reaction rate from 13.3 to 14.7 mu mol per ml packed cells per min. Ne ither the incubation in the dark nor irradiation with laser light caused ch anges of enzyme activity in the presence of chloroaluminium or metal-free p hthalocyanine.