Ferredoxin and ferredoxin reductase activities in bovine thyroid. Possible relationship to iodotyrosine deiodinase.
NADPH-ferredoxin reductase and ferredoxin activities have been identified in bovine thyroid particulate fractions (mainly mitochondria) after ultrasonication and DEAE-cellulose chromatography. The proteins were identified by their ability to reconstitute NADPH-cytochrome c reductase activity when used in combination. NADPH ferredoxin reductase and ferredoxin also catalyzed NADPH-dependent deiodination of L-diiodotyrosine; bovine adrenodoxin and adrenodoxin reductase could partially replace the thyroidal components in NADPH-dependent deiodination of L-diiodotyrosine. Both these reconstitutive activities were substantially inhibited by the iron chelators, alpha, alpha'-dipyridyl and o-phenanthroline. Deiodination by the NADPH-ferredoxin reductase-ferredoxin system was inhibited by the addition of a previously characterized dithionite-responsive flavoprotein iodotyrosine deiodinase (preparation F), isolated and purified from bovine thyroid particulate fractions after solubilization with steapsin. Ferredoxin reductase alone showed dithionite-responsive deiodinase activity and elution profiles of this activity on gel filtration before and after steapsin treatment suggest that preparation F may be a form of ferredoxin reductase modified by steapsin.
D000818:Animals; D002417:Cattle; D004227:Dithionite / Q000494:pharmacology; D005287:Ferredoxin-NADP Reductase / Q000302:isolation & purification / Q000378:metabolism*; D005288:Ferredoxins / Q000302:isolation & purification / Q000378:metabolism*; D007453:Iodide Peroxidase / Q000378:metabolism*; D007700:Kinetics; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D009251:NADPH-Ferrihemoprotein Reductase / Q000302:isolation & purification / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism*; D013053:Spectrophotometry; D013347:Subcellular Fractions / Q000201:enzymology; D013961:Thyroid Gland / Q000201:enzymology*
D005288:Ferredoxins; D004227:Dithionite; D010544:Peroxidases; D007453:Iodide Peroxidase; D005287:Ferredoxin-NADP Reductase; D009247:NADH, NADPH Oxidoreductases; D009251:NADPH-Ferrihemoprotein Reductase