The formation of glutathione (GSH) conjugates, best known from the detoxification of xenobiotics, is a widespread strategy to incorporate sulfur into biomolecules. The biosynthesis of gliotoxin, a virulence factor of the human pathogenic fungus Aspergillus fumigatus, involves attachment of two GSH molecules and their sequential decomposition to yield two reactive thiol groups. The degradation of the GSH moieties requires the activity of the Cys-Gly carboxypeptidase GliJ, for which we describe the X-ray structure here. The enzyme forms a homodimer with each monomer comprising one active site. Two metal ions are present per proteolytic center, thus assigning GliJ to the diverse family of dinuclear metallohydrolases. Depending on availability, Zn, Fe, Fe, Mn, Cu, Co, or Ni ions are accepted as cofactors. Despite this high metal promiscuity, a preference for zinc versus iron and manganese was noted. Mutagenesis experiments revealed details of metal coordination, and molecular modeling delivered insights into substrate recognition and processing by GliJ. The latter results suggest a reaction mechanism in which the two scissile peptide bonds of one gliotoxin precursor molecule are hydrolyzed sequentially and in a given order.
A series of bis(pyrazolyl)methane copper complexes were found to catalyze a fast palladium‐free Sonogashira coupling reaction of several iodoarenes with terminal alkynes such as phenylacetylene, propargyl benzyl ether, and (tert‐butyl‐dimethyl)silylacetylene. These reactions proceed with CuCl2·2H2O (10 mol‐%) under aerobic conditions and the corresponding chelate ligand (10 mol‐%), with its tailored facial coordination mode, is crucial for the success of the reaction. The coupling can also be carried out in water with liquid aryl halides and a phase‐transfer catalyst.
The concentration of platinum group metals (PGM), namely palladium, platinum and rhodium, has increased in all earth spheres, which is mainly due to the worldwide use of automotive catalytic converters containing these metals as active components. Especially high concentrations are therefore found near busy roads and in urban environments where PGM concentrations now have reached a level that has let scientists and engineers think about possibilities to recycle these precious metals in the context of urban mining strategies.
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