Bifunctional protein in carrot contains both aspartokinase and homoserine dehydrogenase activities.
Bifunctional protein in carrot contains both aspartokinase and homoserine dehydrogenase activities.
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DOI：
10.1104/pp.97.4.1323
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发表时间：
1991-12
期刊：
影响因子：
7.4
通讯作者：
Barbara J. Wilson;A. C. Gray;Benjamin F. Matthews
中科院分区：
文献类型：
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作者：
Barbara J. Wilson;A. C. Gray;Benjamin F. Matthews
我们已经纯化了高丝氨酸脱氢酶，并对来自蛋白质消化的多肽片段进行了氨基酸测序。胡萝卜(Daucus Carota)高丝氨酸脱氢酶的氨基酸序列表明，在胡萝卜中，天冬氨酸激酶和高丝氨酸脱氢酶的活性位于同一蛋白质上。天冬氨酸激酶和高丝氨酸脱氢酶存在于双功能蛋白上的额外证据是通过纯化步骤中活性的洗脱和酶特异性凝胶染色技术提供的。对含有天冬氨酸激酶活性的高纯度组分进行天冬氨酸激酶活性、高丝氨酸脱氢酶活性和蛋白质的染色。这些凝胶证实，天冬氨酸激酶活性和高丝氨酸脱氢酶活性存在于同一蛋白质上。这种天冬氨酸激酶和高丝氨酸脱氢酶活性的排列也存在于同一蛋白质上，在大肠杆菌中也发现了这种排列，它有两种双功能酶，天冬氨酸激酶I-高丝氨酸脱氢酶I和天冬氨酸激酶II-高丝氨酸脱氢酶II。胡萝卜细胞悬浮培养物中主要形式的高丝氨酸脱氢酶的氨基酸序列与大肠杆菌Thra基因产物天冬氨酸激酶I-高丝氨酸脱氢酶I的氨基酸序列最相似。
We have purified homoserine dehydrogenase to homogeneity and subjected polypeptide fragments derived from digests of the protein to amino acid sequencing. The amino acid sequence of homoserine dehydrogenase from carrot (Daucus carota) indicates that in carrot both aspartokinase and homoserine dehydrogenase activities reside on the same protein. Additional evidence that aspartokinase and homoserine dehydrogenase reside on a bifunctional protein is provided by coelution of activities during purification steps and by enzyme-specific gel staining techniques. Highly purified fractions containing aspartokinase activity were stained for aspartokinase activity, homoserine dehydrogenase activity, and protein. These gels confirmed that aspartokinase activity and homoserine dehydrogenase activity were present on the same protein. This arrangement of aspartokinase and homoserine dehydrogenase activities residing on the same protein is also found in Escherichia coli, which has two bifunctional enzymes, aspartokinase I-homoserine dehydrogenase I and aspartokinase II-homoserine dehydrogenase II. The amino acid sequence of the major form of homoserine dehydrogenase from carrot cell suspension cultures most closely resembles that of the E. coli ThrA gene product aspartokinase I-homoserine dehydrogenase I.