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Related Experiment Video

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Malic enzyme-based system for transhydrogenation between nicotinamide cofactors.

Haizhao Xue1,2, Yinghan Hu1,2, Aabid Manzoor Shah1

  • 1Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China.

Synthetic and Systems Biotechnology
|October 6, 2025
PubMed
Summary

This study introduces a novel malic enzyme-mediated method for transferring reducing equivalents between nicotinamide adenine dinucleotide (NAD) and nicotinamide cytosine dinucleotide (NCD) cofactors. This approach facilitates cofactor interconversion, offering a new tool for metabolic engineering.

Keywords:
Energy metabolismMalic enzymeNicotinamide cytosine dinucleotideRedox cofactorTranshydrogenation

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Area of Science:

  • Biochemistry
  • Metabolic Engineering
  • Synthetic Biology

Background:

  • Nicotinamide cofactors like NAD and NADP are crucial for cellular redox reactions.
  • A non-natural cofactor, nicotinamide cytosine dinucleotide (NCD), expands the cofactor repertoire.
  • Efficient transfer of reducing equivalents between cofactors remains a metabolic engineering challenge.

Purpose of the Study:

  • To develop a novel strategy for enabling reducing equivalent exchange among different cofactors.
  • To utilize malic enzyme (ME)-mediated transhydrogenation for cofactor interconversion.
  • To demonstrate the feasibility of this approach both in vitro and in vivo.

Main Methods:

  • Employed wild-type and engineered malic enzymes (ME and ME*) favoring different cofactors (NAD, NADP, NCD).
  • Established an in vitro system with NADH, NCD, ME, ME*, and pyruvate to assess cofactor conversion.
  • Implemented the system in NCD-self-sufficient Escherichia coli cells to observe reducing equivalent flux.

Main Results:

  • In vitro experiments showed up to 65% NADH consumption and 57% NCDH generation within 2 hours.
  • In Escherichia coli, the system successfully directed reducing equivalents towards NCDH-linked lactate formation.
  • Demonstrated cofactor interconversion using ME-mediated transhydrogenation.

Conclusions:

  • Developed an effective strategy for regulating intracellular reducing equivalents via cofactor transhydrogenation.
  • The ME-mediated approach provides a novel tool for metabolic engineering and synthetic biology applications.
  • Facilitates the rational transfer of reducing equivalents, overcoming a long-standing challenge.