Tyr78-loop对鱼腥藻来源苯丙氨酸脱氨酶活性的影响
Microbiology(2018)
Abstract
[背景]MIO (Methylidene-imidazol-5-one)依赖型酶中,催化因子Tyr所在Loop(Tyr78-loop)的灵活性显著影响酶学性质.[目的]探讨Tyr78-loop对鱼腥藻来源苯丙氨酸脱氨酶酶活的影响,以提高其反应活性.[方法]将该酶的Tyr78-loop进行分子改造,筛选出酶活提高的突变体,并对突变体的酶学性质进行研究.[结果]突变体S73N、E95V、E95K和S73N/E95K在37℃、pH 8.5下比活分别比原酶提高了34%、30%、18%和35%.蛋白三维结构模拟推测在突变体S73N、E95V和E95K中,位于α螺旋与Tyr78-loop交界处的Asn73、Val95和Lys95与附近氨基酸的氢键作用力数目减少,一定程度上增加了Tyr78-loop的柔性.[结论]Ser73位和Glu95位氨基酸的突变增加了Tyr78-loop的灵活性,提高了苯丙氨酸脱氨酶的酶活.
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