TAILIEUCHUNG - Báo cáo khoa học: Role of peroxidase inhibition by insulin in the bovine thyroid cell proliferation mechanism

Monolayer primary cultures of thyroid cells produce, in the presence of insulin, a cytosolic inhibitor of thyroid peroxi-dase (TPO), lacto peroxidase (LPO), horseradishperoxidase (HRPO) and glutathione peroxidase (GPX). The inhibitor, localized in the cytosol, is thermostable and hydrophylic. Itsmolecularmass is less than2 inhibitoryactivity, resistant to proteolytic and nucleolytic enzymes, disappears with sodium metaperiodate treatment, as an oxidant of carbohydrates, supporting its oligosaccharide structure | Eur. J. Biochem. 271 2607-2614 2004 FEBS 2004 doi Role of peroxidase inhibition by insulin in the bovine thyroid cell proliferation mechanism Leon Krawiec1 Ramon A. Pizarro2 Paula Aphalo Elena M. V. de Cavanagh3 Mario A. Pisarev1 2 4 Guillermo J. Juvenal1 2 Lucia Policastro2 and Laura V. Bocanera2 1 Argentine National Research Council CONICET 2 Department of Radiobiology Argeniíne Attomic Energy .Ommìissonì CNEA 3Department of Physical Chemistry School oof Pharmacy atdl Btochemistry University oB Bunnos Aires and 4Department of Human Biochemistry School of Mndirme University oBBuenos Aíres Bnonos Airss Angentina Monolayer primary cultures of thyroid cells produce in the presence of insulin a cytosolic inhibitor of thyroid peroxidase TPO lacto peroxidase LPO horseradish peroxidase HRPO and glutathione peroxidase GPX . The inhibitor localized in the cytosol is thermostable and hydrophylic. Its molecular mass is less than 2 kDa. The inhibitory activity resistant to proteolytic and nucleolytic enzymes disappears with sodium metaperiodate treatment as an oxidant of carbohydrates supporting its oligosaccharide structure. The presence of inositol mannose glucose the specific inhibition of cyclic AMP-dependent protein kinase and the disappearance of peroxidase inhibition by alkaline phosphatase and a-mannosidase in purified samples confirms its chemical structure as inositol phosphoglycan-like. Purification by anionic interchange shows that the peroxidase inhibitor elutes like the two subtypes of inositol phosphoglycans IPG P and A characterized as signal transducers of insulin action. Insulin significantly increases the concentration of the peroxidase inhibitor in a thyroid cell culture at 48 h. The addition of both isolated substances to a primary thyroid culture produces after 30 min a significant increase in hydrogen peroxide H2O2 concentration in the medium concomitantly with the disappearance of the GPX activity in the same .

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