Abstract
A high glutathione peroxidase activity toward phospholipid hydroperoxides is present in rat testis. The attribution of this activity to the selenoenzyme phospholipid hydroperoxide glutathione peroxidase (PHGPX) was supported by cross-reactivity with antibodies raised against pig heart PHGPX which had been purified and characterized. Rat testis PHGPX is partially cytosolic and partially linked to nuclei and mitochondria. The soluble and organelle-bound enzymes appear identical by Western blot analysis. PHGPX, but neither selenium-dependent nor non-selenium-dependent glutathione peroxidase activity, is expressed in testes only after puberty, disappears after hypophysectomy, and is partially restored by gonadotropin treatment. Specific immunostaining of testes by antiserum against PHGPX appears as a fine granular brown pattern localized throughout the cytoplasm in more immature cells but is confined to the peripheral part of the cytoplasm, the nuclear membrane, and mitochondria in maturating spermatogenic cells. As expected, immunostaining of spermatogenic cells in hypophysectomized animals was negative, but gonadotropin treatment only marginally increased the immunoreactivity. The expression of PHGPX in testes is consistent with the previously described specific requirement for selenium for synthesis of a 15-20-kDa selenoprotein which is related to the production of functional spermatozoa.
Highlights
From the $Department of Biological Chemistry, University of Padova, §Institute of Histology and Embriology, University of Pavia, and Wnstitute of Chemistry, University of Udine, Italy
Selenium-dependent glutathione peroxidasaectivity, is While pholipid hydroperoxide glutathione peroxidase (PHGPX) has been formerly characterized by its expressed intestes only afterpuberty, disappearsafter activity on phospholipid hydroperoxides [12], it has been hypophysectomy, andis partially restored by gonado- recently shown to reduce cholesterol hydroperoxides [13]
In this report we present enzymological and immunohistocheman inframe TGA codon: glutathione peroxidase (GPX)’ [4], ical evidence for a high expression of PHGPX in rat testes glycosylated extracellular glutathione peroxidase [5], phos- which appears to be gonadotropin-dependent and suggests a pholipid hydroperoxide glutathione peroxidase (PHGPX) [6], specific role for this enzyme in the overall process of sperand type I iodothyronine deiodinase [7,8,9]
Summary
Antonella RoveriS, AndreCa asascoS, Matilde MaiorinoSP, aolo DalanS, Albert0CalligaroQ, and Fulvio UrsiniSV. Selenium-dependent glutathione peroxidasaectivity, is While PHGPX has been formerly characterized by its expressed intestes only afterpuberty, disappearsafter activity on phospholipid hydroperoxides [12], it has been hypophysectomy, andis partially restored by gonado- recently shown to reduce cholesterol hydroperoxides [13]. In this report we present enzymological and immunohistocheman inframe TGA codon: glutathione peroxidase (GPX)’ [4], ical evidence for a high expression of PHGPX in rat testes glycosylated extracellular glutathione peroxidase [5], phos- which appears to be gonadotropin-dependent and suggests a pholipid hydroperoxide glutathione peroxidase (PHGPX) [6], specific role for this enzyme in the overall process of sperand type I iodothyronine deiodinase [7,8,9]. Contain at least two molecularly characterized Sedependent glutathione peroxidases; these being GPX [10]
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