| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2002: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2001: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2000: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
Distribution of free and combined D-amino acids in marine diatoms and freshwater microalgae was measured. And variation in D-amino acids content under various culture conditions of diatom, Asterionella sp. was examined. Furthermore, the origin of D-amino acids in microalgae was researched.
1. The presence of free D-aspartate and D-alanine was verified in diatoms, Asterionella sp., Thalassiola sp., Nitzschia sp., and Pseudo-nitzschia sp. D-Aspartate was also found in fresh water microalgae, Botrydiopsos alpina, Chlorella pyeniodos, C.vulgaris and Scenedesumus obliquus, but D-alanine was not detected in these species.
2. The content of D-alanine varied by growth phase : D-Alanine content of Asterionella sp. increased in stationary phase and decreased in extinction phase.
3. Combined form of D-aspartate, D-glutamate and D-alanine were detected in the residue of diatoms after extracting with 80% ethanol, but D-alanine was not detected in freshwater microalgae.
4. Alanine racemase activity was detected in the marine diatom, Thalassiosira sp. which was cultured germ-free. Optimal pH of this enzyme was extremely high, about 9.5 and the Km value (substrate L-alanine) was 19.7 mM. The enzyme did not require pyridoxal 5'-phosphate (PLP) as a cofactor in the reaction. These results suggest that alanine racemase from Thalassiosira sp. bindes PLP more tightly as a cofactor compared with bacterial enzyme.
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