ABSTRACT
This chapter discusses the photodynamic action of sensitizers on some enzymes and membranes, also in combination with hyperthermia, with special emphasis on the mechanisms that lead to functional disturbances. The catalytic activity of most enzymes is lost upon photodynamic treatment, although the intrinsic sensitivity differs widely. The photodynamic action of sensitizers upon glyceraldehyde-3-phosphate dehydrogenase has perhaps been studied in more detail than any other enzyme. An interesting example of the photodynamically induced inhibition of a chain or cluster of enzymes is the inhibition of the DNA excision repair system in L929 cells. Photodynamically induced damage of the plasma membrane has been implicated in cell death, especially after short incubation times with sensitizers, whereas, after prolonged incubation times, damage to intracellular parameters becomes relatively more important. Photodynamically induced damage of the plasma membrane has been implicated in cell death, especially after short incubation times with sensitizers, whereas, after prolonged incubation times, damage to intracellular parameters becomes relatively more important.
