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標題: 嗜鹽性甲烷菌之相容質-glycinebetaine的合成相關酵素及其影響因子之研究
The regulatory factors of glycinebetaine synthetic associated enzymes in Methanohalophilus strain FDF1
作者: 楊道任
Yang, Daw-Renn
關鍵字: Methanohalophilus;嗜鹽性甲烷菌;Archaea;compatible solute;glycinebetaine;古生菌;相容質;甜菜鹼
出版社: 植物學系
嗜鹽性甲烷菌 Methanohalophilus strain FDF1 是株自高鹽生態環境下
betaine的合成相關酵素及其影響因子。於strain FDF1的細胞萃取液添
加 [methyl14C]S-adenosyl-L-methionine(SAM) 作為甲基提供者時,可
形成 14C標定的 sarcosine、N,N-dimethylglycine 和 glycinebetaine
。証實 glycinebetaine 生化合成路徑和 13CNMR 分析結果相符合,乃由
glycine經甲基化而形成 glycinebetaine。高濃度鉀離子( 800mM KCl
),會促進 sarcosine 和 glycinebetaine 的形成;反之,隨著鉀離子濃
度減少, sarcosine 和 glycinebetaine 的生成累積逐漸減少至無。顯
示鉀離子濃度的高低,會影響 glycinebetaine 生化合成的正逆向反應。
以 14C- glycine 探討 glycinebetaine 合成的第一個產物sarcosine的
形成酵素 glycine N-methyltransferase,結果顯示添加 20ug蛋白的細
胞萃取液,在四小時的反應時間下,能產生最多量的 sarcosine。於定量
外,氧氣的存在,並不會抑制由 glycine 生成 sarcosine 的酵素反應。
在含20ug蛋白的細胞萃取液中,添加 800mM 的 KCl、2mM 的 glycine
和 4.6mM 的 SAM,於 37℃、四小時的反應條件下, glycine N-
methyltransferase的比活性是 290 nmol/。

Methanohalophilus strain FDF1 was an anaerobic archaea isolated
from the hypersaline environment. Cells accumulated glycine-
betaine, beta-glutamine and N-acetyl-beta-lysine as the major
compatible solutes to survive in the high salt environment.
Among the organic solutes, glycinebetaine has been demonstrated
with the highest osmoprotective efficiency. This investigate
analyzed the glycinebetaine synthetic pathway and studied the
regulatory factors which involved in the glycinebetaine
synthetic enzymes. With the addition of [methyl14C]S-adenosyl-L-
methionine(SAM) into the crude extract of Methanohalophilus
strain FDF1 as methyl donor, 14C labeled sarcosine, N,N-
dimethylglycine and glycine- betaine were formed. This result
demonstrated that the pathway of glycinebetaine synthesis
proceeded from the methylation of glycine as indicated by
13CNMR analysis. The addition of potassium chloride (up to
800mM) increased the formation of sarcosine and glycinebetaine.
In contrast, low and none potassium addition enhanced the
reversed process. The concentration of potassium may play an
important role in the glycinebetaine synthesis. The assay
conditions for the sarcosine forming enzyme, glycine N-
methyltransferase were set up. With the addition of 14C-
glycine, the highest amount of sarcosine formed under the 20 ug
protein of the crude extract of strain FDF1 in 4 hours reaction
time. This enzyme was not sensitive to the oxygen. The optimal
enzyme assay condition of glycine N-methyltransferase reached a
specific activity as 290 nmol/ after 4 hr reaction with
the addition of 800 mM KCl, 2 mM glycine and 4.6 mM SAM into 20
ug protein of strain FDF1 crude extract at 37℃.
Appears in Collections:生命科學系所

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