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PubMed2007

Investigation of the mechanism of action of pyrogallol-phloroglucinol transhydroxylase by using putative intermediates.

Pyrogallol-phloroglucinol transhydroxylase from Pelobacter acidigallici, a molybdopterin-containing enzyme, catalyzes a key reaction in the anaerobic degradation of aromatic compounds. In vitro, the enzymatic reaction requires 1,2,3,5-tetrahydroxybenzene as a cocatalyst and the transhydroxylation occurs without exchange with hydroxy groups from water. To test our previous proposal that the transfer of the hydroxy group occurs via 2,4,6,3',4',5'-hexahydroxydiphenyl ether as an intermediate, we synthesized this compound and investigated its properties. We also describe the synthesis and characterization of 3,4,5,3',4',5'-hexahydroxydiphenyl ether. Both compounds could substitute for the cocatalyst in vitro. This indicates that the diphenyl ethers can intrude into the active site and initiate the catalytic cycle. Recently, the X-ray crystal structure of the transhydroxylase (TH) was published16 and it supports the proposed mechanism of hydroxy-group transfer.

Anaerobiosis↗
PubMed2006

Molecules at close range: encapsulated solvent molecules in pyrogallol[4]arene hexameric capsules.

[reaction: see text] Pyrogallol[4]arenes form hexameric capsules with a large cavity and can be regarded as nanoreactors. The (1)H NMR signals of the encapsulated chloroform and benzene molecules are very complex, which may indicate that these encapsulated molecules are trapped in slightly different capsules. Co-encapsulation was found to be favored, and the ASIS effect was found to be enhanced, probably due to the close proximity and the higher molecular fraction of the benzene/chloroform complex in the capsule.

Journal Article↗
PubMed2005

Nano-dimensions for the pyrogallol[4]arene cavity.

The cup-like cavity of pyrogallol[4]arenes has been deepened by the addition of four hydrogen bonded bipyridine molecules to the upper-rim of the calixarene, enabling the extended cup-like molecules to stack inside one another and consequently trap and completely enshroud a single guest molecule within the 250 angstroms3 cavitand formed between two of these stacked "nano-cups".

Journal Article↗
PubMed2004

Crystal structure of pyrogallol-phloroglucinol transhydroxylase, an Mo enzyme capable of intermolecular hydroxyl transfer between phenols.

The Mo enzyme transhydroxylase from the anaerobic microorganism Pelobacter acidigallici catalyzes the conversion of pyrogallol to phloroglucinol. Such trihydroxybenzenes and their derivatives represent important building blocks of plant polymers. None of the transferred hydroxyl groups originates from water during transhydroxylation; instead a cosubstrate, such as 1,2,3,5-tetrahydroxybenzene, is used in a reaction without apparent electron transfer. Here, we report on the crystal structure of the enzyme in the reduced Mo(IV) state, which we solved by single anomalous-diffraction technique. It represents the largest structure (1,149 amino acid residues per molecule, 12 independent molecules per unit cell), which has been solved so far by single anomalous-diffraction technique. Tranhydroxylase is a heterodimer, with the active Mo-molybdopterin guanine dinucleotide (MGD)(2) site in the alpha-subunit, and three [4Fe-4S] centers in the beta-subunit. The latter subunit carries a seven-stranded, mainly antiparallel beta-barrel domain. We propose a scheme for the transhydroxylation reaction based on 3D structures of complexes of the enzyme with various polyphenols serving either as substrate or inhibitor.

Bacteria, Anaerobic↗
PubMed2003

Kinetic determination of traces of iodide by its catalytic effect on oxidation of sodium pyrogallol-5-sulfonate by hydrogen peroxide.

The kinetic method is based on a catalytic effect on the oxidation of sodium pyrogallol-5-sulfonate by hydrogenperoxide. The reaction is followed spectrophotometrically at 436.8 nm. The kinetic parameters of the reaction are reported and a rate equation is suggested. The calibration graph is linear in the range 10-200 ng cm(-3). The effects of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method. This method has high sensitivity and good selectivity when anions are concerned as well. That is why it can be successfully applied to determination of iodide in real samples (mineral water and soil) directly after the elimination of cations, which interfere. The method was applied to determine iodide in natural waters and soil.

Journal Article↗