Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.10.3.2 (laccase)
 4,656 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Low-temperature EPR spectroscopy with frequencies between 95 and 345 GHz and magnetic fields up to 12 T has been used to study metal sites in proteins or inorganic complexes and free radicals. The high-field EPR method was used to resolve g-value anisotropy by separating it from overlapping hyperfine couplings. The presence of hydrogen bonding interactions to the tyrosyl radical oxygens in ribonucleotide reductases were detected. At 285 GHz the g-value anisotropy from the rhombic type 2 Cu(II) signal in the enzyme laccase has its g-value anisotropy clearly resolved from slightly different overlapping axial species. Simple metal site systems with S>1/2 undergo a zero-field splitting, which can be described by the spin Hamiltonian. From high-frequency EPR, the D values that are small compared to the frequency (high-field limit) can be determined directly by measuring the distance of the outermost signal to the center of the spectrum, which corresponds to (2 S-1)* mid R: Dmid R: For example, D values of 0.8 and 0.3 cm(-1) are observed for S=5/2 Fe(III)-EDTA and transferrin, respectively. When D values are larger compared to the frequency and in the case of half-integer spin systems, they can be obtained from the frequency dependence of the shifts of g(eff), as observed for myoglobin in the presence ( D=5 cm(-1)) or absence ( D=9.5 cm(-1)) of fluoride. The 285 and 345 GHz spectra of the Fe(II)-NO-EDTA complex show that it is best described as a S=3/2 system with D=11.5 cm(-1), E=0.1 cm(-1), and g(x)= g(y)= g(z)=2.0. Finally, the effects of HF-EPR on X-band EPR silent states and weak magnetic interactions are demonstrated.
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PMID:Examples of high-frequency EPR studies in bioinorganic chemistry. 1258 59

Cryptococcus neoformans secretes 3-hydroxyanthranilate (3HAA), but the utility is unknown. Exogenous 3HAA promoted growth of cultures starved for iron with transferrin, presumably by releasing Fe(III) reductively. Exogenous 3HAA protected C. neoformans from strong oxidants, suggesting a role in resistance to killing by immune cells. 3HAA represents an endogenous laccase substrate, in that crude laccase preparations convert 3HAA to cinnabarinic acid, whereas 3HAA concentrations are higher in Lac- mutants. We isolated hypersecreting mutants as highly fluorescent clones. Because C. neoformans has been isolated from rotting wood, we looked for a role in degradation of lignin. Using cyclic voltammetry, we found no electrochemical evidence that organic oxidation products of 3HAA are capable of oxidizing lignin. We found neither cellulose dehydrogenase nor lignin peroxidase enzymic activity, nor did C. neoformans grow on cellulose as carbon source. We found no evidence for production of Fenton reagent by cultures, even in the presence of transition metal ions or of those and 3HAA. The biological utility of 3HAA may be related to its functions as reducing agent and, conceivably, as laccase substrate. It does not appear to attack wood, nor does C. neoformans appear to have a mechanism to rot wood.
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PMID:3-Hydroxyanthranilate in Cryptococcus neoformans: a secreted reductant that does not enable wood rot. 1296 24