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Updated: Aug 2, 2025

Simultaneous Measurement of Superoxide/Hydrogen Peroxide and NADH Production by Flavin-containing Mitochondrial Dehydrogenases
Published on: February 24, 2018
Competitive inhibition of a non-natural cofactor dependent formaldehyde dehydrogenase by imidazole
Junting Wang1,2, Li Wan1,2, Xiaojia Guo1
1Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China.
Objectives:
To better understand the unique inhibitory behavior of a non-natural cofactor preferred formaldehyde dehydrogenase (FalDH) mutant 9B2.
Results:
We described our serendipitous observation that 9B2 was reversibly inhibited by residual imidazole introduced during protein preparation, while the wild-type enzyme was not sensitive to imidazole. Kinetic analysis showed that imidazole was a competitive inhibitor of formaldehyde with a Ki of 16 μM and an uncompetitive inhibitor of Nicotinamide Cytosine Dinucleotide for 9B2, indicating that formaldehyde and imidazole were combined in the same position. Molecular docking results of 9B2 showed that imidazole could favorably bind very close to the nicotinamide moiety of the cofactor, where formaldehyde was expected to reside for catalysis, which was in line with a competitive inhibition.
Conclusion:
The mutant 9B2 can be competitively inhibited by imidazole, suggesting that cautions should be taken to evaluate activities as protein mutants might attain unexpected sensitivity to a component in buffers for purification or activity assays.
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