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pp.263-271
We checked the presence of phospholipase A2(PLA)2 which could split the ester bond at the position 2 in the glycerol backbone of glycerophospholipids, in the cells of hyperthermophiles of Pyrococcus horikoshii and Sulfolobus acidocaldarius. The results obtained are as follows; (1). Pyrococcus horikoshii cells were grown in obligate anaerobic conditions at 95℃ and they needed sulfur as energy source instead of oxygen, while Sulfolobus acidocaldarius species grew well in the aerobic medium (pH 2.5) containing yeast and sucrose at 75℃. (2). Pyrococcus horikoshii cells produced phospholipase A2 in the cell culture media although this species did not show lipase activity at least in the pH range of 1.5 ~ 3.5. Sulfolobus acidocaldarius cells produced lipase hydrolyzing triacylglycerols such as triolein, but did not split any kind of phospholipids used as substates. (3). The compound of 1-decanoyl-2-(p-nitrophenylglutaryl) phosphatidylcholine was not suitable for a substrate in this experiment, though frequently used as a subtrate for checking presence of phospholipase A2, for its decomposi-tion in this experiment. The L-α-phosphatidylcholine-β-[N-7-nitrobenz-2-oxa-1, 3-diazol]aminohexanoyl-γ-hexadecanoyl labelled with a fluorescent material, did not show any migration of acyl chains in the molecule during the reaction with phospholipase A2 under a hot condition. (4). Phospholipase A2 in the cells of Pyrococcus horikoshii, showed the optimum activity at pH6.7~7.2 and 95~105℃, respectively, and was activated by addition of calcium chloride solution. Andthe phospholipase A2 specifically hydrolyzed glycero-phospholipids such as phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl serine and phosphatidyl inositol, but could not split phospholipid containing ether bonds in the molecule such as DL -α-phosphatidylcholine-β-palmitoyl-γ-O-hexadecyl, DL-α-phosphati- dylcholine-β- oleoyl-γ-O-hexadecyl, DL-phosphatidylcholine-dihexadecyl.
