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<p>Carcinine, a bioactive compound with antioxidant and anti-glycation properties, holds significant promise for applications in pharmaceuticals and cosmetics. This study demonstrates a novel strategy for the direct biosynthesis of carcinine from low-cost L-histidine and β-alanine using a multi-enzyme cascade system. A highly efficient histidine decarboxylase (PphHDC) was identified. Following vector optimization and induction parameter tuning, soluble expression of PphHDC was systematically enhanced in the BPH-2 strain (BL21(DE3) harboring pACYC-<i>Pphhdc</i>) under optimal conditions: 37&#xa0;°C, 0.1&#xa0;mM IPTG, and 8&#xa0;h induction. Further, the optimally expressed PphHDC achieved the optimal enzymatic activity of 7.76 U/mg under conditions of pH 6.0, 30&#xa0;°C, and 5&#xa0;mM Ca<sup>2</sup>⁺. To facilitate carcinine synthesis, PphHDC was integrated with the previously reported SGE (Sfp-GSG-Ebony) enzyme in three catalytic systems: single-cell, dual-cell whole-cell catalysis, and multi-enzyme cascade. Among these, the multi-enzyme cascade system, comprising purified soluble PphHDC and SGE-D<sub>N</sub> (engineered with an N-terminal DsbA tag to enhance solubility), achieved the highest efficiency. This system produced a maximum carcinine titer of 4.29&#xa0;mM with a yield of 0.18&#xa0;mM/h within 24&#xa0;h, representing the highest reported conversion from L-histidine and β-alanine. These findings establish a robust foundation for cost-effective industrial production of carcinine. The study highlights the importance of fine-tuning heterologous expression systems to balance protein solubility and productivity in biocatalytic applications.</p>

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Identification of histidine decarboxylase and its multi-enzyme cascade system for cost-efficient biosynthesis of carcinine

  • 期刊论文

  • 发表日期：

    2025年8月25日

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  • Man Zhao,
  • Zhenhao Jiang,
  • Mengying Yu,
  • Zhiqiang Liu,
  • Yuguo Zheng

摘要

Carcinine, a bioactive compound with antioxidant and anti-glycation properties, holds significant promise for applications in pharmaceuticals and cosmetics. This study demonstrates a novel strategy for the direct biosynthesis of carcinine from low-cost L-histidine and β-alanine using a multi-enzyme cascade system. A highly efficient histidine decarboxylase (PphHDC) was identified. Following vector optimization and induction parameter tuning, soluble expression of PphHDC was systematically enhanced in the BPH-2 strain (BL21(DE3) harboring pACYC-Pphhdc) under optimal conditions: 37 °C, 0.1 mM IPTG, and 8 h induction. Further, the optimally expressed PphHDC achieved the optimal enzymatic activity of 7.76 U/mg under conditions of pH 6.0, 30 °C, and 5 mM Ca2⁺. To facilitate carcinine synthesis, PphHDC was integrated with the previously reported SGE (Sfp-GSG-Ebony) enzyme in three catalytic systems: single-cell, dual-cell whole-cell catalysis, and multi-enzyme cascade. Among these, the multi-enzyme cascade system, comprising purified soluble PphHDC and SGE-DN (engineered with an N-terminal DsbA tag to enhance solubility), achieved the highest efficiency. This system produced a maximum carcinine titer of 4.29 mM with a yield of 0.18 mM/h within 24 h, representing the highest reported conversion from L-histidine and β-alanine. These findings establish a robust foundation for cost-effective industrial production of carcinine. The study highlights the importance of fine-tuning heterologous expression systems to balance protein solubility and productivity in biocatalytic applications.