Characterization of iodothyronine sulfotransferase activity in the cytosol of Rana catesbeiana tadpole tissues.

We have investigated the sulfation of thyroid hormones (THs) in the cytosol from Rana catesbeiana tadpole tissues. Sulfation of 3,3',5-triiodothyronine (T(3)) by the liver cytosol, which was dependent on protein amount, incubation time, and temperature, suggested the presence of TH sulfotransferases (SULTs) in the liver. The apparent Michaelis-Menten constant (K(m)) of the liver cytosol was 0.

In vitro thyroid hormone-disrupting activity in effluents and surface waters in Thailand.

The thyroid hormone (TH)-disrupting activity of effluents and environmental water samples in Thailand was surveyed by three in vitro bioassays with different endpoints. These assays test the potency of competitive binding with the active form of TH, 3,3',5-[(125)I]triiodo-l-thyronine (T(3)), to the plasma transport protein transthyretin (TTR) and TH receptor (TR; the TTR assay and TR assay, respectively) and the interference with the cellular T(3)-signaling pathway through TR-mediated luciferase gene activation (the luc assay). The TH-disrupting activity in water samples collected from paper manufacturing plants (PMPs), the canal Khlong U-Taphao, and a sewage-treatment plant (STP) was detected predominantly in the dichloromethane/methanol or methanol fractions of solid-phase extraction, suggesting a similar hydrophobic nature of the causative contaminants.

Uncompetitive inhibition of Xenopus laevis aldehyde dehydrogenase 1A1 by divalent cations.

Aldehyde dehydrogenases (ALDHs) convert aldehydes into their corresponding carboxylic acids. ALDH1A1, also known as ALDH class 1 (ALDH1) or retinaldehyde dehydrogenase (RALDH1), prefers retinal to acetaldehyde as a substrate. To investigate the effects of divalent cations on the dehydrogenase activity of Xenopus laevis ALDH1A1, the formation of acetate and retinoic acid from acetaldehyde and retinal, respectively, was investigated in the presence of Ca2+, Mg2+, Mn2+ or Zn2+.