RESEARCH STUDY ON THE DISTRIBUTION OF D-AMINO ACIDS AND D-AMINO ACID RACEMASE IN MICROALGAE

微藻中D-氨基酸和D-氨基酸消旋酶的分布研究

基本信息

批准号：
12660189
负责人：
NAGAHISA Eizo
金额：
$ 1.98万
依托单位：
Kitasato University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

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.

测量了海洋硅藻和淡水微藻中游离和结合的 D-氨基酸的分布。以及硅藻、Asterionella sp.不同培养条件下D-氨基酸含量的变化。被检查了。并对微藻中D-氨基酸的来源进行了研究。 1．在硅藻、Asterionella sp.、Thalassiola sp.、Nitzschia sp. 和 Pseudo-nitzschia sp. 中证实了游离 D-天冬氨酸和 D-丙氨酸的存在。淡水微藻、高山葡萄孢、小球藻、普通藻和斜生栅藻中也发现了D-天门冬氨酸，但在这些物种中未检测到D-丙氨酸。2． D-丙氨酸含量因生长阶段而异：Asterionella sp. 的 D-丙氨酸含量。稳定期增加，消光期减少。3．硅藻经80%乙醇提取后的残渣中检测到D-天门冬氨酸、D-谷氨酸和D-丙氨酸的复合形式，而淡水微藻中未检测到D-丙氨酸。4．在海洋硅藻 Thalassiosira sp. 中检测到丙氨酸消旋酶活性。这是无菌培养的。该酶的最适pH值极高，约为9.5，Km值（底物L-丙氨酸）为19.7 mM。该酶不需要 5'-磷酸吡哆醛 (PLP) 作为反应中的辅助因子。这些结果表明来自 Thalassiosira sp. 的丙氨酸消旋酶。与细菌酶相比，作为辅助因子，PLP 结合更紧密。