Enhancement of catalytic activity by gene truncation: activation of L-aspartase from Escherichia coli.
Enhancement of catalytic activity by gene truncation: activation of L-aspartase from Escherichia coli.
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通过基因截断增强催化活性：激活大肠杆菌的 L-天冬氨酸酶。
DOI：
10.1006/bbrc.1997.7294
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Viola,RE
中科院分区：
文献类型：
--
作者：
Jayasekera,MM;Saribas,AS;Viola,RE
大肠杆菌天冬氨酸酶通过羧基末端的蛋白水解而激活。已经进行了系统的研究，目的是确定该区域中的氨基酸，影响酶的催化活性。终止密码子已经被引入到不同的位置，通过顺序地消除该区域中的每个极性和带电氨基酸来过早地截短编码天冬氨酸酶的theaspA基因。酶对其底物天冬氨酸的亲和力随着每个功能上重要的氨基酸被消除而系统地降低。然而，增强的催化活性（高达2.5倍thekat为天然酶），观察到那些截短突变体，在一个带正电荷的羧基末端氨基酸结束。已经确定了蛋白水解酶激活的精确位置，并且已经证明这种共价激活不依赖于也观察到的蛋白水解酶的变构激活。
Aspartase fromEscherichia coliis activated by proteolysis at the carboxy-terminal. A systematic study has been undertaken with the goal of identifying the amino acids in this region that influence the catalytic activity of aspartase. Stop codons have been introduced at various positions to prematurely truncate theaspAgene that encodes for aspartase by sequentially eliminating each of the polar and charged amino acids in this region. The affinity of the enzyme for its substrate aspartic acid decreases systematically as each functionally significant amino acid is eliminated. However, enhanced catalytic activity (up to 2.5 times thekcatfor native aspartase) is observed for those truncation mutants that end in a positively charged carboxy-terminal amino acid. The precise position of the proteolytic activation of aspartase has been defined, and this covalent activation has been shown to be independent of the allosteric activation of aspartase that is also observed.