Mutagenic activity of river water from a river near textile industrial complex in Korea

The mutagenic activity of XAD-2 adsorbates and water extracts recovered from nine locations of the Kumho River was tested on S. typhimurium TA98 strain to identify the source of the mutagenicity. A sampling site, receiving effluents from the textile industrial complex located in Daegu City, showed extraordinarily high mutagenic activity, especially in the presence of S9 mixture, at all sampling time in both XAD-2 adsorbates and dichloromethane extracts. This indicated the existence of the frame-shift mutagens in the Kumho River, same type of mutagens detected in previous studies by other researchers in the Nakdong River into which the Kumho River discharges. The fractionation study showed that the mutagenic chemicals in the river water are mid-polar. Furthermore, mean tail length obtained by single cell gel electrophoresis assay (Comet assay) showed consistent dose-dependent DNA damage, indicating that the chemicals in the river water not only act as frame-shift mutagens but also break human lymphocytes DNA strain. Chemical identification of the mutagens should be require

Probing the Role of Sigma π Interaction and Energetics in the Catalytic Efficiency of Endo-1,4-β-Xylanase

Chaetomium globosum endo-1,4-β-xylanase (XylCg) is distinguished from other xylanases by its high turnover rate (1,860 s(−1)), the highest ever reported for fungal xylanases. One conserved amino acid, W48, in the substrate binding pocket of wild-type XylCg was identified as an important residue affecting XylCg's catalytic efficiency

An amino acid at position 142 in nitrilase from Rhodococcus rhodochrous ATCC 33278 determines the substrate specificity for aliphatic and aromatic nitriles

Nitrilase from Rhodococcus rhodochrous ATCC 33278 hydrolyses both aliphatic and aromatic nitriles. Replacing Tyr-142 in the wild-type enzyme with the aromatic amino acid phenylalanine did not alter specificity for either substrate. However, the mutants containing non-polar aliphatic amino acids (alanine, valine and leucine) at position 142 were specific only for aromatic substrates such as benzonitrile, m-tolunitrile and 2-cyanopyridine, and not for aliphatic substrates. These results suggest that the hydrolysis of substrates probably involves the conjugated π-electron system of the aromatic ring of substrate or Tyr-142 as an electron acceptor. Moreover, the mutants containing charged amino acids such as aspartate, glutamate, arginine and asparagine at position 142 displayed no activity towards any nitrile, possibly owing to the disruption of hydrophobic interactions with substrates. Thus aromaticity of substrate or amino acid at position 142 in R. rhodochrous nitrilase is required for enzyme activity

A case of amoxicillin-induced hepatocellular liver injury with bile-duct damage

Amoxicillin, an antibiotic that is widely prescribed for various infections, is associated with a very low rate of drug-induced liver injury; hepatitis and cholestasis are rare complications. Here we present a case of a 39-year-old woman who was diagnosed with abdominal actinomycosis and received amoxicillin treatment. The patient displayed hepatocellular and bile-duct injury, in addition to elevated levels of liver enzymes. The patient was diagnosed with amoxicillin-induced cholestatic hepatitis. When amoxicillin was discontinued, the patient's symptoms improved and her liver enzyme levels reduced to near to the normal range