The ct-subunit primary structure of cyclic GMP phosphodiesterase has been determined by parallel analysis of the protein amino acid sequence and the corresponding cDNA nucleotide sequence. The enzyme ~t-subunit contains 858 amino acid residues, its N-terminal amino group being acetylated. The partial primary structure of the enzyme fl-subunit has also been elucidated. A significant homology has been found between the ct-and fl-subunits of cGMP phosphodiesterase.

We have isolated a novel secretory 28-kDa protein which is an abundant component of the rat olfactory mucosa. The partial sequence of the 28-kDa protein has been determined. The amino acid sequence of the 28-kDa protein is similar to that of non-selenium glutathione peroxidase from bovine ciliary body. The 28-kDa protein catalyzed decomposition of the hydrogen peroxide as well as organic hydroperoxides by reduced glutathion and seems to be a member of the glutathion peroxidases family.

Peroxiredoxins are a novel family of antioxidant proteins that specifically prevent enzymes from metal-catalyzed oxidation. The localization of a member of the mono-cystein subfamily of peroxiredoxins, the 28-kDa protein, in different rat tissues and its antioxidant properties were investigated. By immunoblotting, the 28-kDa peroxiredoxin was found to be most highly concentrated in olfactory epithelium and present in all tissues tested (skin, lung, trachea, kidney, womb, and brain). Immunostaining with rabbit polyclonal antibody raised against the 28-kDa peroxiredoxin revealed the particularly high level of the 28-kDa peroxiredoxin immunoreactivity in air-contacting areas (apical regions and mucus of the olfactory and respiratory epithelium and skin epidermis), which are continually exposed to numerous air-borne reactive oxygen species. In the apical regions of the olfactory and respiratory epithelium, the 28-kDa-peroxiredoxin immunogold labeling outlined microvilli and cilia and was mainly located in sustentacular cells and in respiratory and goblet cells, as electron-microscopic analysis revealed. In skin epidermis, the 28-kDa peroxiredoxin immunoreactivity was confined to the granular layer and specifically concentrated in sebaceous glands of hair follicle. In situ hybridization with 33P-labeled antisense RNA probe revealed the expression of the 28-kDa peroxiredoxin mRNA in tissues with a high level of the 28-kDa peroxiredoxin immunoreactivity. Immunodepletion of the 28-kDa peroxiredoxin profoundly decreased the antioxidant activity of the olfactory tissue extract.

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cDNA clones encoding the 45 kDa protein were isolated from a rat olfactory epithelium cDNA library and their inserts were sequenced. The reconstructed protein sequence comprises 400 amino acids with a calculated molecular mass of 46 026 Da. A homology was revealed between the amino acid sequence of the 45 kDa protein and the proteins involved in the transfer of hydrophobic ligands. Using in situ hybridisation, the 45 kDa protein mRNA expression was detected in the layer of supportive cells of olfactory epithelium, apical region of trachea, surface layer of the ciliated bronchial epithelium in lung and in skin epidermis.z 1999 Federation of European Biochemical Societies.