Photodynamic Damage to Yeast Subcellular Organelles Induced by Elevated Levels of Endogenous Protoporphyrin IX

The 2,2"-dipyridyl-induced accumulation of protoporphyrin IX in Saccharomyces cerevisiae cells was shown to be accompanied by the photoinhibition of cell respiration and the enhancement of the photoinduced permeability of plasma membranes to the fluorescent dye primuline. The visible-light illumination (at 400–600 nm) of the mitochondria and plasma membranes isolated from yeast cells with a high level of endogenous protoporphyrin IX intensified lipid peroxidation in these subcellular organelles. Comparative studies showed that the rad 52 mutant cells, which are deficient in the postreplicative recombinational DNA repair system, are considerably more sensitive to the inactivating action of visible light than are the wild-type cells and the rad 3 mutant cells, which are deficient in the excision DNA repair system. The contribution of photodynamic damage to the yeast subcellular organelles to the lethal photodynamic effect is discussed.     

Fluorescent photobleaching of endogenous protoporphyrin IX in yeast cells

Yeast Saccharomyces cerevisiae accumulate in the presence of chelator 2,2'-dipyridyl, two fractions of photosensitizer protoporphyrin IX, which fluoresce with maxima at 625 and 635 nm. The two fractions were found to differ from each other in the dynamics and character of fluorescence photobleaching. In contrast to the protoporphyrin IX that fluoresces with a maximum at 625 nm, the protoporphyrin IX fraction that fluoresces with a maximum at 635 nm is more photolable; in addition, upon photobleaching of its fluorescence, a new maximum at 675 nm appears.     

Photodynamic damage of yeast subcellular fraction induced by elevated levels of endogenous protoporphyrin IX

The 2,2'-dipyridyl-induced accumulation of protoporphyrin IX in Saccharomyces cerevisiae cells was shown to be accompanied by the photoinhibition of cell respiration and the enhancement of the photoinduced permeability of plasma membranes to the fluorescent dye primuline. The visible-light illumination (at 400-600 nm) of the mitochondria and plasma membranes isolated from yeast cells with a high level of endogenous protoporphyrin IX intensified lipid peroxidation in these subcellular organelles. Comparative studies showed that the rad 52 mutant cells, which are deficient in the postreplicative recombinational DNA repair system, are considerably more sensitive to the inactivating action of visible light than are the wild-type cells and the rad 3 mutant cells, which are deficient in the excision DNA repair system. The contribution of photodynamic damage to the yeast subcellular organelles to the lethal photodynamic effect is discussed.     

Synthesis of protoporphyrin IX induced by 5-aminolevulinic acid in yeast cells in the presence of 2,2;-dipyridyl

5-Aminolevulinic acid (ALA), a precursor of porphyrin synthesis, increased the production of various porphyrin compounds in Candida guilliermondii cells. Metalloporphyrins and protoporphyrin IX (PPIX) were predominantly accumulated, respectively, at ALA concentrations of 0.2-0.4 mM and at those higher than 1.5 mM. 2,2;-Dipyridyl which complexed with bivalent metals significantly increased the content of endogenous PPIX even at ALA concentrations lower than 0.5 mM. Under these conditions, the yeast sensitivity to photodynamic effect of visible light (400-600 nm) dramatically increased due to photosensitization by endogenous PPIX.