Fluorescence excitation- and emission spectra indicate the presence of pterin(s) and flavin(s) in isolated flagella of the phytoflagellate Euglena gracilis. These compounds appear to bind at least in part non-covalently to the molecular framework of the paraflagellar body, which is the presumed photoreceptor organelle and which is attached to the isolated flagella. A compound with pterin-like fluorescence excitation and emission spectrum could he extracted with methanol from isolated flagella and could he recovered on thin-layer silica gels. Besides the previously assumed photoreceptor function of flavins, our results suggest also a role for pterins in the photosensory transduction chain of Euglena gracilis.
5-Aminolevulinic acid (ALA) is a heme precursor that accumulates in lead poisoning and inborn porphyrias. It has been shown to produce reactive oxygen species upon metal-catalyzed aerobic oxidation and to cause oxidative damage to proteins, liposomes, DNA, and subcellular structures. Studies have also shown that ALA may condense to yield the cyclic product 3,6-dihydropyrazine-2,5-dipropanoic acid (DHPY). Here we propose that DHPY could be involved in DNA damage in the presence of high concentrations of ALA. Exposure of plasmid pUC19 DNA to low concentrations of DHPY (2-10 microM) in the presence of 0.1 mM Cu2+ ions causes DNA strand breaks, as demonstrated by agarose gel electrophoresis. It was also shown that in the presence of Cu2+ ions DHPY is able to increase the oxidation of monomeric 2'-deoxyguanosine to form 8-oxo-7,8-dihydro-2'-deoxyguanosine as inferred from high performance liquid chromatography measurements using electrochemical detection. Addition of a metal chelator (bathocuproine, 0.5 mM), the DNA compacting polyamines spermidine (1 mM) and spermine (1 mM) or antioxidant enzymes such as superoxide dismutase (10 microg/ml) and catalase (20 pg/ml) protect the DNA against these damages. The data presented here are discussed with respect to the increased frequency of liver cancer in patients with acute intermittent porphyria.
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