1992-05-22
Species differences in liver type I iodothyronine deiodinase
Publication
Publication
Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology , Volume 1121 - Issue 1-2 p. 160- 166
The type I iodothyronine deiodinase (ID-I) of liver is an important enzyme for the conversion of the prohormone thyroxine (T4) to the active thyroid hormone 3,3′,5-triiodothyronine (T3). Because it is an integral membrane protein of low abundance, purification of ID-I from rat liver has proven to be difficult. We have analyzed ID-I in liver microsomal fractions from various animals to reveal possible species differences and to explore alternative sources for the isolation of the enzyme. ID-I was characterized by enzyme assay with 3,3′,5′-triiodothyronine (rT3) as the preferred substrate and by affinity-labeling with N-bromoacetyl-[125I]T3 (BrAc[125I]T3). Labeled ID-I subunit was identified and quantified by SDS-PAGE and autoradiography. The Mr of ID-I in the species investigated varied between 25.7 and 29.1 kDa. Rat and dog liver microsomes had a markedly higher enzyme content than microsomes of human, mouse, rabbit, cow, pig, sheep, goat, chicken or duck liver. Rat liver microsomes showed the highest ID-I activity of all species examined. Turnover numbers for ID-I varied between 264 and 1059 min−1, with rabbit and goat showing the highest values. However, dog liver ID-I displayed an exceptionally low turnover number of 78 min−1. In conclusion, ID-I has similar properties in all species examined with the notable exception of dog.
| Additional Metadata | |
|---|---|
| , , , , , , | |
| doi.org/10.1016/0167-4838(92)90349-I, hdl.handle.net/1765/74080 | |
| Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology | |
| Organisation | Department of Internal Medicine |
|
Schoenmakers, C., Pigmans, I. G. A. J., & Visser, T. (1992). Species differences in liver type I iodothyronine deiodinase. Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology, 1121(1-2), 160–166. doi:10.1016/0167-4838(92)90349-I |
|
