5'-Iodothyronine deiodinase of rat liver: activity in microsomes prepared by various methods, solubilization by detergents and partial purification.

Iodothyronine deiodinase activities of rat liver microsomes prepared by (1) differential centrifugation, (2) column chromatography, (3) precipitation with Ca2+, (4) precipitation at low pH, or combinations of these were compared. Method 2 or 2 followed by 4 provided microsomes with specific activities 4.6- and 7.4-times higher than method 1, respectively. Both Triton X-100 at 0.1% (w/v) and 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate (Chaps) at 4-6 mM efficiently solubilized deiodinase and were not inhibitory at low concentrations. The Chaps-soluble enzyme could be moderately purified by fractionation with ammonium sulfate but more effectively with poly(ethylene glycol).