Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P04040 (Catalase)
 3,577 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Catalase-peroxidases (KatG) are bifunctional heme peroxidases with an overwhelming catalatic activity. The structures show that the buried heme b is connected to the exterior of the enzyme by a main channel built up by KatG-specific loops named large loop LL1 and LL2, the former containing the highly conserved sequence Met-Gly-Leu-Ile-Tyr-Val-Asn-Pro-Glu-Gly. LL1 residues Ile248, Asn251, Pro252, and Glu253 of KatG from Synechocystis are the focus of this study because of their exposure to the solute matrix of the access channel. In particular, the I248F, N251L, P252A, E253Q, and E253D mutants have been analyzed by UV-visible and resonance Raman spectroscopies in combination with steady-state and presteady-state kinetic analyses. Exchange of these residues did not alter the kinetics of cyanide binding or the overall peroxidase activity. Moreover, the kinetics of compound I formation and reduction by one-electron donors was similar in the variants and the wild-type enzyme. However, the turnover numbers of the catalase activity of I248F, N251L, E253Q, and E253D were only 12.3, 32.6, 25, and 42% of the wild-type activity, respectively. These findings demonstrate that the oxidation reaction of hydrogen peroxide (not its reduction) was affected by these mutations. The altered kinetics allowed us to monitor the spectral features of the dominating redox intermediate of E253Q in the catalase cycle. Resonance Raman data and structural analysis demonstrated the existence of a very rigid and ordered structure built up by the interactions of these residues with distal side and also (via LL1) proximal side amino acids, with the heme itself, and with the solute matrix in the channel. The role of Glu253 and the other investigated channel residues in maintaining an ordered matrix of oriented water dipoles, which guides hydrogen peroxide to its site of oxidation, is discussed.
 ...
PMID:Role of the main access channel of catalase-peroxidase in catalysis. 1624 60

Biomarkers of oxidative stress metabolism and the innate immune response were examined in gill and head kidney tissue of wild-caught yellow perch (Perca flavescens) collected from four sites ranging in type and degree of metal pollution in the St. Lawrence River, Quebec, Canada. Sites were ranked as follows: Ile Dorval<Iles aux Sables<Ilet Vert<Beauharnois. Biomarker measurements did not correspond completely to the perceived pollution gradient. Total protein content was highest at a site 4 km downstream of municipal effluents (Ilet Vert) exposed to moderate and high levels of heavy metals and faecal coliforms, respectively. Thiol content was highest at the reference site (Ile Dorval) with the lowest contaminant levels. Glutathione-S-transferase (GST) activity was highest in fish from the site furthest downstream that was exposed to moderate metal contamination (Iles aux Sables). Glutathione reductase (GRd) activity was high in both gill and head kidney tissue of fish from the reference site (Ile Dorval) and highest in the kidney of fish from the most contaminated site (Beauharnois). Catalase activity was highest in head kidney tissue in fish from this latter site. Ceruloplasmin activity was lowest in head kidney from fish collected at the reference site and highest at Beauharnois. Lysozyme activity was lowest in head kidney tissue from fish at the reference site and highest in tissue from fish at Ilet Vert, downstream of municipal effluents. These results suggest that the direction and magnitude of oxidative stress biomarker response and innate immune function biomarker response vary between tissues and among complex mixtures of contaminants, complicating interpretation of results. Results further suggest that bacterial loading, as measured by faecal coliforms, affects the oxidative stress metabolism and the innate immune response.
 ...
PMID:Gill and head kidney antioxidant processes and innate immune system responses of yellow perch (Perca flavescens) exposed to different contaminants in the St. Lawrence River, Canada. 1899 21