Taxonomic and functional turnover are decoupled in European peat bogs

In peatland ecosystems, plant communities mediate a globally significant carbon store. The effects of global environmental change on plant assemblages are expected to be a factor in determining how ecosystem functions such as carbon uptake will respond. Using vegetation data from 56 Sphagnum-dominated peat bogs across Europe, we show that in these ecosystems plant species aggregate into two major clusters that are each defined by shared response to environmental conditions. Across environmental gradients, we find significant taxonomic turnover in both clusters. However, functional identity and functional redundancy of the community as a whole remain unchanged. This strongly suggests that in peat bogs, species turnover across environmental gradients is restricted to functionally similar species. Our results demonstrate that plant taxonomic and functional turnover are decoupled, which may allow these peat bogs to maintain ecosystem functioning when subject to future environmental change

Thiotaurine prevents apoptosis of human neutrophils: a putative role in inflammation

Thiotaurine, a metabolic product of cystine, contains a sulfane sulfur atom that can be released as H2S, a gaseous molecule with a regulatory activity on inflammatory responses. The influence of thiotaurine on human leukocyte spontaneous apoptosis has been evaluated by measuring caspase-3 activity in human neutrophils. Addition of 100 μM thiotaurine induced a 55% inhibition of caspase-3 activity similar to that exerted by 100 μM H2S. Interestingly, in the presence of 1 mM GSH, an increase of the inhibition of apoptosis by thiotaurine has been observed. These results indicate that the bioactivity of thiotaurine can be modulated by GSH, which promotes the reductive breakdown of the thiosulfonate generating H2S and hypotaurine. As thiotaurine is able to incorporate reversibly reduced sulfur, it is suggested that the biosynthesis of this thiosulfonate could be a means to transport and store H2S

Hypotaurine and superoxide dismutase: protection of the enzyme against inactivation by hydrogen peroxide and peroxidation to taurine

Hypotaurine is able to prevent the inactivation of SOD by H2O2. The protection is concentration-dependent: at 20 mM hypotaurine the inactivation of SOD is completely prevented. It is likely that hypotaurine exerts this effect by reacting with hydroxyl radicals, generated during the inactivation process, in competition with the sensitive group on the active site of the enzyme. According to this, spectral studies indicate that in presence of hypotaurine the integrity of the active site of SOD is preserved by the disruptive action of H2O2 An interesting outcome of the SOD/H2O2/hypotaurine interaction is that SOD catalyzes the peroxidation of hypotaurine to taurine. Indeed, the formation of taurine increases with the reaction time and with the enzyme concentration. Although the peroxidase activity of SOD is not specific and relatively slow compared to the dismutation of superoxide, it might represent another valuable mechanism of production of taurine

Sulfur-containing cyclic ketimines and imino acids. A novel family of endogenous products in the search for a role.

Aminoethylcysteine, lanthionine, cystathionine and cystine are mono-deaminated either by l-amino-acid oxidase or by a transaminase exhibiting the properties described for glutamine transaminase. The deaminated products cyclize producing the respective ketimines. Authentic samples of each ketimine were prepared by reacting the appropriate aminothiol compound with bromopyruvate, except cystine ketimine which required the interaction of thiopyruvate with cystine sulfoxide. Reduction of the first three mentioned ketimines with NaBH4 yields the respective derivatives with the saturated rings of thiomorpholine and hexahydrothiazepine. The same reduction is carried out enzymically by a reductase extracted from mammalian tissues. Properties of the members of this family of compounds are described. Gas chromatography followed by mass spectrometry permits the identification of most of these products. HPLC is very useful for the determination of the ketimines by taking advantage of specific absorbance at 380 nm obtained by prior derivatization with phenylisothiocyanate. Adaptation of these and other analytical procedures to biological samples disclosed the presence of most of these compounds in bovine brain and in human urine. By using [35S]lanthionine ketimine as a representative member of the ketimine group, the specific, high-affinity, saturable and reversible binding to bovine brain membranes has been demonstrated. The binding is removed by aminoethylcysteine ketimine and by cystathionine ketimine indicating the occurrence in bovine brain of a common binding site for ketimines. The reduced ketimines are totally ineffective in competing with [35S]lanthionine ketimine. Alltogether these findings are highly indicative for the existence in mammals of a novel class of endogenous sulfur-containing cyclic products provided with a possible neurochemical function to be investigated further

Proline-glutamate chimeras in isopeptides. Synthesis and biological evaluation of conformationally restricted glutathione analogues

The two novel diastereoisomeric glutathione analogues 1 and 2 have been designed and synthesized by replacing the native gamma-glutamylic moiety with the conformational rigid skeleton of cis- or trans-4-carboxy-L-proline residue. Both analogues have been obtained by following the solution phase peptide chemistry methodologies and final reduction of the corresponding disulfide forms 13 and 14. The two analogues 1 and 2 have been tested towards gamma-glutamyltranspeptidase (gamma-GT) and human glutathione S-transferase (hGST P1-1). Both analogues 1 and 2 are completely resistant to enzymatic degradation by gamma-GT. The S-transferase utilizes the analogue 2 as a good substrate while is unable to bind the analogue 1

Proline-glutamate chimeras in isopeptides. Synthesis and biological evaluation of conformationally restricted glutathione analogues

The two novel diastereoisomeric glutathione analogues 1 and 2 have been designed and synthesized by replacing the native gamma-glutamylic moiety with the conformational rigid skeleton of cis- or trans-4-carboxy-L-proline residue. Both analogues have been obtained by following the solution phase peptide chemistry methodologies and final reduction of the corresponding disulfide forms 13 and 14. The two analogues 1 and 2 have been tested towards gamma-glutamyltranspeptidase (gamma-GT) and human glutathione S-transferase (hGST P1-1). Both analogues 1 and 2 are completely resistant to enzymatic degradation by gamma-GT. The S-transferase utilizes the analogue 2 as a good substrate while is unable to bind the analogue 1

Vanin-1(−/−) Mice Exhibit a Glutathione-Mediated Tissue Resistance to Oxidative Stress

Vanin-1 is an epithelial ectoenzyme with pantetheinase activity and generating the amino-thiol cysteamine through the metabolism of pantothenic acid (vitamin B(5)). Here we show that Vanin-1(−/−) mice, which lack cysteamine in tissues, exhibit resistance to oxidative injury induced by whole-body γ-irradiation or paraquat. This protection is correlated with reduced apoptosis and inflammation and is reversed by treating mutant animals with cystamine. The better tolerance of the Vanin-1(−/−) mice is associated with an enhanced gamma-glutamylcysteine synthetase activity in liver, probably due to the absence of cysteamine and leading to elevated stores of glutathione (GSH), the most potent cellular antioxidant. Consequently, Vanin-1(−/−) mice maintain a more reducing environment in tissue after exposure to irradiation. In normal mice, we found a stress-induced biphasic expression of Vanin-1 regulated via antioxidant response elements in its promoter region. This process should finely tune the redox environment and thus change an early inflammatory process into a late tissue repair process. We propose Vanin-1 as a key molecule to regulate the GSH-dependent response to oxidative injury in tissue at the epithelial level. Therefore, Vanin/pantetheinase inhibitors could be useful for treatment of damage due to irradiation and pro-oxidant inducers