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At least 325 records · Page 18Linked to original sources
PubMed1988

Accumulation of photodynamic tetrapyrroles induced by acifluorfen-methyl.

Treatment with acifluorfen-methyl (AFM), methyl 5-(2-chloro-4-[tri-fluoromethyl] phenoxy)-2-nitrobenzoate, inhibited protochlorophyllide synthesis in dark-held, delta-amino levulinic acid-fed, excised cotyledons of cucumber (Cucumis sativus L.). Protochlorophyllide and protoporphyrin IX levels in AFM-treated cotyledons were inversely related and dependent on AFM concentration; as the herbicide dose increased, protoporphyrin IX levels also increased with a concomitant loss of protochlorophyllide. Significant protoporphyrin IX accumulation was induced by concentrations of AFM from the linear region of the membrane disruption dose response curve. The pattern of precursor accumulation seen in HPLC chromatograms from extracts of AFM-treated tissue indicate that Mg insertion into the tetrapyrrole ring is inhibited, suggesting interference with Mg-chelatase. An inhibitor of delta-amino levulinic acid synthesis, gabaculine (3-amino-2,3-dihydrobenzoic acid), completely blocked the membrane disruption activity of AFM in illuminated cotyledons. Protoporphyrin IX accumulating in AFM-treated tissues may serve as the primary photosensitizer for initiating lipid peroxidation.

Journal Article↗
PubMed1982

Effects of delta-aminolaevulinic acid, porphobilinogen and structurally related amino acids on 2-deoxy-glucose uptake in cultured neurons.

The effects of delta-aminolaevulinic acid (ALA), porphobilinogen (PBG), gamma amino-butyric acid (GABA), muscimol, glutamic acid and kainic acid on [3H]2-deoxy-D-glucose uptake by cultured neurons were investigated. Exposure to the cultures for 4 days, to ALA at concentrations as low as 10 microM caused a significant, dose-dependent decrease in [3H] 2-deoxy-D-glucose uptake. Neither ALA nor PBG appeared to interfere directly with glucose transport into the neuron but 1 mM ALA caused an initial stimulation of [3H] 2-deoxy-D-glucose uptake which increased to a maximum after 4 hr and fell to below control values after 19 hr exposure. GABA and muscimol caused similar increases in [3H] 2-deoxy-D-glucose uptake but these values remained above control levels after 19 hr exposure. Glutamic acid and kainic acid caused an immediate increase in [3H] 2-deoxy-D-glucose uptake which declined to minimum values after 4 hr exposure. The effect of ALA on glucose utilization in neurons may be of particular relevance to patients with acute porphyria where a genetic lesion in neural haem and haemoprotein biosynthesis is postulated to occur. ALA appeared to be more toxic to the neurons than any of the other compounds tested, possibly causing a critical depletion of energy reserves and cell death.

Aminolevulinic Acid↗
PubMed1987

Identification of an intermediate of delta-aminolevulinate biosynthesis in Chlamydomonas by high-performance liquid chromatography.

The first committed intermediate of the chlorophyll biosynthetic pathway is delta-aminolevulinic acid (ALA). In plant cells, ALA is formed from glutamate by a pathway not yet clearly defined. One of the proposed pathways involves the reduction of glutamate to glutamate-1-semialdehyde (GSA) via a glutamyl-tRNA intermediate. GSA is then converted to ALA by an aminotransferase. We are studying this pathway using partially purified components from Chlamydomonas reinhardtii in in vitro reactions with [3H]L-glutamate as the substrate and analysis of the radioactive reaction products via HPLC. In reactions either lacking GSA-aminotransferase or containing gabaculine (an inhibitor of aminotransferase), a radioactive intermediate is formed which cochromatographs with synthetic GSA. As observed previously for ALA synthesis, the synthesis of this intermediate has an absolute requirement for RNA, ATP, and active enzymes, while the requirement for NADPH is less stringent. Both the accumulated intermediate and the synthetic GSA can be converted to ALA by the aminotransferase without any additional substrates or cofactors. These results support previous observations that GSA or a very similar compound is an intermediate of ALA synthesis.

Aminolevulinic Acid↗