抄録
A hypocalcemic protein was isolated for the first time from porcine parotid gland by the procedures of aqueous extraction, precipitation at pH 4.8, ammonium sulfate fractionation, chromatography on DEAE-cellulose, and repeated gel filtration on Sephadex G-200. The purified protein lowered the serum-calcium concentration in albino rabbits by 12.5±1.3% at a dose of 20μg/kg body weight 4-6 hr after the injection. The purified protein was found to be homogeneous, being a single band by polyacrylamide gel electrophoresis and by analytical ultracentrifugation. The molecular weight of the porcine hypocalcemic protein was determined to be 52000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Amino acid analysis revealed that the protein was rich in aspartic and glutamic acids and in leucine, and that the ratio of acidic/basic amino acid residues was 2.13, and the ratio of histidine/lysine was 3.07 in this protein. The latter ratio is characteristic, since the ratio is below 1.00 in many proteins. The chemical properties of the porcine parotid hypocalcemic protein were slightly different from that of the bovine parotid hypocalcemic protein, although they were similar in biological effect.
