Ca2+ regulation of thyroid NADPH-dependent H2O2 generation.
A thyroid particulate fraction contains an NADPH-dependent H2O2-generating enzyme which requires Ca2+ for activity. A Chaps solubilized extract of the thyroid particulate fraction partially purified by DEAE chromatography did not show a dependence on Ca2+ for activity. Preincubation of the particulate fraction with Ca2+ yielded a preparation insensitive to Ca2+. The non-particulate fraction obtained after incubation of the particles in the presence of Ca2+ was able to inhibit, in the presence of EGTA, the Ca2+-desensitized particulate fraction and the enzyme isolated on DEAE. It is concluded that the reversible Ca2+ activation of the NADPH-dependent H2O2 generation was modulated in porcine thyroid tissue by (a) calcium-releasable inhibitor protein(s).
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002793:Cholic Acids; D004533:Egtazic Acid / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009249:NADP / Q000494:pharmacology*; D019255:NADPH Oxidases; D012995:Solubility; D013552:Swine; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*
D002793:Cholic Acids; D004533:Egtazic Acid; D009249:NADP; D006861:Hydrogen Peroxide; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; C028213:3-((3-cholamidopropyl)dimethylammonium)-1-propanesulfonate; D002118:Calcium