title: The primary structure of porcine Cu-Zn superoxide dismutase. Evidence for allotypes of superoxide dismutase in pigs.
abstract: Cu-Zn superoxide dismutase was purified to homogeneity from mixed pig blood and from a single pig. The isolated product had an absorption ratio 280/260 nm of 0.91, a specific activity of 3 000 +/- 200 units (cytochrome c reduction test), and an isoelectric point of 7.5 (chromatofocusing) or 7.25 (isoelectric focusing), respectively. Sequence determination was performed by automated solid-phase Edman degradation of fragments of the reduced S-carboxymethylated proteins obtained by digestion with trypsin or Staphylococcus aureus proteinase V8 or treatment with cyanogen bromide. Acetylation of the N-terminus was confirmed by comparing high performance liquid chromatography retention times of N-terminal peptides with those of authentic samples. Sequencing of the superoxide dismutase of mixed porcine blood revealed heterogeneity (70% Leu; 30% Val at position 29), whereas the sample derived from a single French pig proved to be homogeneous (100% Leu at position 29). The complete sequence of pig superoxide dismutase comprised 152 amino-acid residues, which corresponds to a theoretical molecular mass of 15 800 Da per subunit, and exhibited the expected high homology with those of other mammals. The aspartate and all 7 histidine residues known to complex the metal ions in bovine superoxide dismutase are conserved in the porcine sequence at the homologous positions Asp82 and His45, His47, His62, His70, His79, His119, respectively.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D002417:Cattle; D003300:Copper; D006801:Humans; D010446:Peptide Fragments / Q000302:isolation & purification; D013482:Superoxide Dismutase / Q000235:genetics; D013552:Swine; D015032:Zinc
chemical_list: D010446:Peptide Fragments; D003300:Copper; D013482:Superoxide Dismutase; D015032:Zinc