Descripción: The possible involvement of apoplastic reactive oxygen species produced by the oxidation of free polyamines in the leaf growth of salinized maize has been studied here. Salt treatment increased the apoplastic spermine and spermidine levels, mainly in the leaf blade elongation zone. The total activity of polyamine oxidase was up to 20-fold higher than that of the copper-containing amine oxidase. Measurements of H2O2, ·O2-, and HO· production in the presence or absence of the polyamine oxidase inhibitors 1,19-bis- (ethylamine)-5,10,15 triazanonadecane and 1,8-diamino-octane suggest that, in salinized plants, the oxidation of free apoplastic polyamines by polyamine oxidase by would be the main source of reactive oxygen species in the elongation zone of maize leaf blades. This effect is probably due to increased substrate availability. Incubation with 200 μM spermine doubled segment elongation, whereas the addition of 1,19-bis-(ethylamine)-5,10,15 triazanonadecane and 1,8-diamino-octane to 200 μM spermine attenuated and reversed the last effect, respectively. Similarly, the addition of MnCl2 (an ·O2- dismutating agent) or the HO· scavenger sodium benzoate along with spermine, annulled the elongating effect of the polyamine on the salinized segments. As a whole, the results obtained here demonstrated that, under salinity, polyamine oxidase activity provides a significant production of reactive oxygen species in the apoplast which contributes to 25-30% of the maize leaf blade elongation.

Descripción: The pathways for putrescine biosynthesis and the effects of polyamine biosynthesis inhibitors on the germination and hyphal development of Gigaspora rosea spores were investigated. Incubation of spores with different radioactive substrates demonstrated that both arginine and ornithine decarboxylase pathways participate in putrescine biosynthesis in G. rosea. Spermidine and spermine were the most abundant polyamines in this fungus. The putrescine biosynthesis inhibitors α-difluoromethylarginine and α-difluoromethylornithine, as well as the spermidine synthase inhibitor cyclohexylamine, slightly decreased polyamine levels. However, only the latter interfered with spore germination. The consequences of the use of putrescine biosynthesis inhibitors for the control of plant pathogenic fungi on the viability of G. rosea spores in soil are discussed. © 2003 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.

Descripción: Trypanosomatid parasites containing a metabolically unstable ornithine decarboxylase (ODC) are naturally resistant to high levels of α-difluoromethylornithine (DFMO) because this ODC inhibitor, though causing a drastic reduction of intracellular putrescine, elicits only a moderate decrease of the spermidine endogenous pool. In this study we have used a combination of DFMO with cyclohexylamine (CHA; bis-cyclohexylammonium sulfate), an inhibitor of spermidine synthase, to reach a more complete depletion of spermidine. Under these conditions we have observed the arrest of proliferation not only in trypanosomatids with stable ODC but also in parasites with an enzyme of high turnover rate. In all cases the reinitiation of proliferation occurred only after the addition of exogenous spermidine, and neither putrescine nor spermine were able to induce the same effect. © 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.

Descripción: The aggregation of α-synuclein is characteristic of Parkinson's disease (PD) and other neurodegenerative synucleinopathies. The 140-aa protein is natively unstructured; thus, ligands binding to the monomeric form are of therapeutic interest. Biogenic polyamines promote the aggregation of α-synuclein and may constitute endogenous agents modulating the pathogenesis of PD. We characterized the complexes of natural and synthetic polyamines with α-synuclein by NMR and assigned the binding site to C-terminal residues 109-140. Dissociation constants were derived from chemical shift perturbations. Greater polyamine charge (+ 2 → + 5) correlated with increased affinity and enhancement of fibrillation, for which we propose a simple kinetic mechanism involving a dimeric nucleation center. According to the analysis, polyamines increase the extent of nucleation by ∼104 and the rate of monomer addition ∼40-fold. Significant secondary structure is not induced in monomeric α-synuclein by polyamines at 15°C. Instead, NMR reveals changes in a region (aa 22-93) far removed from the polyamine binding site and presumed to adopt the β-sheet conformation characteristic of fibrillar α-synuclein. We conclude that the C-terminal domain acts as a regulator of α-synuclein aggregation.