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A special bifunctional enzyme from Alcaligenes sp. DN25 and its enzymatic degradation of cyanide
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  • Qingyun Li,
  • Yexing Yin,
  • Huanji Chen,
  • Xiaoxian He,
  • Yongqiang He,
  • Haibo Liu,
  • Youyan Liu
Qingyun Li
Guangxi University
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Yexing Yin
Guangxi University
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Huanji Chen
Guangxi University
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Xiaoxian He
Guangxi University
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Yongqiang He
Guangxi University
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Haibo Liu
Guangxi University
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Youyan Liu
Guangxi University
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Abstract

Deepening and expanding the understanding of cyanide-degrading enzymes are the foundation of developing new technology for cyanide bioremediation. In this study, a putative cyanide-degrading enzyme gene from Alcaligenes sp. DN25(CGMCC 5734) was cloned and expressed in Escherichia coli. The purified recombinant enzyme named as cdE, consisting of a 38-kDa polypeptide, showed 99% amino acid sequence identity with cyanidase derived from Pseudomonas stutzeri AK61. However, the cdE was supposed to have both cyanide dihydratase (CynD) and cyanide hydratase (CHT) activities based on the findings that formate, ammonium and formamide were simultaneously generated during cyanide enzymatic degradation. The enzymatic properties of cdE were characterized with an optimal activity at a temperature of 30°C, pH of 7.0, and could even maintain approximately 50% activity at pH 9.0. More importantly, the selectivity of enzymatic reaction pathway was suggested related to the conformation stability of the cdE that affected by the modifications of amino acids near the active site as well as the degradation conditions, leading to produce different ratios of formate and formamide. As far as we know, this is the first report of a cyanide-degrading enzyme possessing bifunctional catalysis activity, which might become a supplement of cyanide-degrading enzyme databases.