Complex sentence: The enzymatic activity of iodotyrosine deiodinase has also been known to exist in the tissues of the liver and kidneys as well; however, the physiological significance of these findings is not yet clear.
Split into simpler sentences: The enzymatic activity of iodotyrosine deiodinase has also been known to exist in the tissues of the liver and kidneys as well. However, the physiological significance of these findings is not yet clear.