Deiodinase enzyme activity measurements
Deiodinase enzymes (D1, D2 and D3) play a fundamental role in tissue thyroid hormone (TH) economy by activating (mainly D2) or inactivating (mainly D3) the hormones by eliminating an iodine group from the molecule. Therefore, measuring deiodinase activity is crucial to characterize tissue TH action.
Although determining the expression level of D2 is a common way to characterize the intracellular activation of TH, this can often be inaccurate due to the complex posttranslational regulation of the enzyme. Uniquely in Hungary, our laboratory routinely measures D2 activity in animal and human samples using 125I isotope-labelled substrate.
Measuring D3 activity requires a complex approach involving separation of radioactive analytes with liquid chromatography. Our laboratory has is equipped with a cutting edge high-pressure liquid chromatography (HPLC) system with a photodetector that is able to detect 125I isotope radiation. This equipment enables the measurement of different TH forms in parallel that is suitable not only for determining D3 activity, but to investigate in vivo deiodination as well.
Due to our methodologies, our laboratory is counted among the few workshops of the continent that are capable of measuring all known characteristics of tissue TH metabolism in house. Furthermore, we are part of the European Thyroid Association consortium for standardizing the measurement of TH metabolism.