Photodynamically induced changes of acetylcholinesterase activity from human erythrocytes

The light and photodynamic actions on acetylcholinesterase activity from human erythrocytes were studied. After light irradiation (670 nm, semiconducting low power laser) the maximum reaction rate increased from 13.3 to 14.8 mumol per ml packed cells per min for an energy dose 9 J, and above that dose it decreased (10.8 mumol per ml packed cells per min for an energy dose of 15 J). The Michaelis-Menten constant changed in the opposite direction. After irradiation of erythrocyte suspension in the presence of zinc phthalocyanine 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 mumol per ml packed cells per min. Similarly, the Michaelis-Menten constant decreased reaching 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 mumol per ml packed cells per min. Neither the incubation in the dark nor irradiation with laser light caused changes of enzyme activity in the presence of chloroaluminium or metal-free phthalocyanine.