| Summary: | Author describe a method of extraction and partial purification of phospho-proteins from Oyster, Crassostrea gigas. The extraction of the phosphoproteins was carried out with hot water and with 0.02M NaHCO3 solution containing 5% NaCl. The Oyster, Crassostrea gigas contained two kinds of phosphoproteins in the hot water extracts (P-1, P-2) and three kinds of phosphoproteins in the alkaline soluble extracts (P-3, P-4 and P-5). The amino acid compositions of the phosphoproteins of the hot water extracts were characterized by relatively high percentage for glutamic acid and aspartic acid. The amino acid compositions of the each phosphoproteins of the alkaline soluble extracts were characterized by relatively high percentage for glutamic acid and threonine. The phosphono-compounds was found in the all phosphoproteins. It has been demonstrated that the peak 1, 2, 3, 4 and 5 contained the phosphonoproteins and that about 78%, 50%, 82%, 72% and 51% as phosphonate-phosphorus of total phosphorus. The inhibition of angiotensin 1 converting enzyme (ACE) by the five phosphoproteins was investigated in vitro. The IC50 values of these phosphoproteins (P-1～P-5) for ACE were 1.43, 0.27, 0.45, 0.33 and 0.17, respectively. The peak 5 had the most inhibition activity and showed 0.17 (mg protein / ml) inhibition against ACE at IC50 value. 長崎大学教育学部自然科学研究報告. vol.55, p.49-57; 1996 departmental bulletin paper
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