Expression of type I iodothyronine 5'-deiodinase in Xenopus laevis oocytes.
The enzymes mediating the conversion of thyroxine to 3,5,3'-triiodothyronine have proved difficult to purify and characterize biochemically. In this report we describe the successful expression in Xenopus laevis oocytes of type I iodothyronine 5'-deiodinase. Oocytes injected with rat liver mRNA and then incubated for 5 days demonstrated a progressive increase in 5'-deiodinase activity. This activity: (a) manifested a Km for 3,3',5'-triiodothyronine of 0.24 microM, (b) was sensitive to inhibition by 6-n-propyl-2-thiouracil, and (c) was associated with the membrane fraction of oocyte homogenates. Size fractionation of the mRNA by agarose gel electrophoresis under non-denaturing conditions resulted in the identification of a 1.5-2.0-kilobase fraction capable of inducing type I 5'-deiodinase activity. This oocyte assay system should provide a mechanism for identifying cDNA(s) encoding the enzymes involved in the peripheral metabolism of thyroid hormones.
St Germain
D L
DL
Department of Medicine and Physiology, Dartmouth Medical School, Hanover, New Hampshire 03756.
Morganelli
C M
CM
D000818:Animals; D004587:Electrophoresis, Agar Gel; D005260:Female; D005786:Gene Expression Regulation; D007453:Iodide Peroxidase / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008297:Male; D008970:Molecular Weight; D009865:Oocytes / Q000201:enzymology*; D011061:Poly A / Q000235:genetics; D011441:Propylthiouracil / Q000494:pharmacology; D012313:RNA / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D014284:Triiodothyronine / Q000378:metabolism; D014285:Triiodothyronine, Reverse / Q000378:metabolism; D014982:Xenopus laevis
D012333:RNA, Messenger; D014284:Triiodothyronine; D011061:Poly A; D014285:Triiodothyronine, Reverse; D012313:RNA; D011441:Propylthiouracil; D007453:Iodide Peroxidase