α-天门冬氨酰二肽酶及其进化酶的FT-IR研究

FT-IR STUDIES OF α-ASPARTYL DIPEPTIDASE AND ITS EVOLUTIONAL ENZYME

用分子定向进化技术 ,在酶活力和热稳定性双重选择压力下 ,筛选到了一株Kcat/KM 是天然酶47倍的进化酶。用FT -IR方法 ,测定了α -天门冬氨酰二肽酶及其进化酶的酰胺I带图谱 ,定量估算了天然酶和进化酶的各种二级结构含量。天然酶中 ,β折叠结构含量为28.5 % ,α螺旋结构含量为33 % ,这与园二色谱测量α螺旋结构为33 %的结果有很好的一致 ,剩余的残基形成不同类型的转角和无规结构 ,其总含量为38.5 %。在进化酶中 ,β折叠结构含量为26.8 % ,α螺旋结构含量为31 % ,其它结构为不同类型的转角和无规结构,含量为42.2 %

Under double screen pressure of specific activity and thermo stablity, an evolved α-aspartyl dipeptidase,with 47 folds higher activity than its wild type ancestor,was obtained. By using FT-IR, the secondary structure of α-aspartyl dipeptidase and its evolutional enzyme were studied. It is found that α-helix structure is 31%,β-sheet content is 26.8% while turn and random coil component are 42.2% in the evolutional type of α-aspartyl dipeptidase .In the wild type enzyme, α-helix structure is 33%, β-sheet content is 28.5% and turn and random coil are 38.5%.These structure changes lead to arise the flexibility of evolutional type and adaptability to substrate.