Succinate dehydrogenase (SDH) is an enzyme complex that is a cytochrome oxidase. And, it is present in the inner mitochondrial membrane of many bacterial cells and eukaryotes. In addition, it is part of the tricarboxylic acid (TCA) and respiratory electron transport chain. SDH can provide electrons to the aerobic and energy-producing respiratory chain of eukaryotic mitochondria and many prokaryotic cells. So, it can be a marker enzyme of mitochondria. SDH consists of a heterochromatic protein complex consisting of four subunits encoded by the nuclear genome, two hydrophilic and two hydrophobic. Of these, the flavoprotein subunit (SDHA) and iron-sulfur subunit (SDHB) form the catalytic structural domain. Besides, hydrophobic membrane-anchored subunits SDHC and SDHD anchor the complexes to the inner mitochondrial membrane.

SDH catalyzes the sixth step of the TCA cycle, namely the oxidation of succinate to fumarate and the reduction of ubiquinone to panthenol. And, the enzyme uses FAD as its hydrogen acceptor for the offloaded electrons, not NAD⁺. Importantly, it allows the FADH2 produced during the oxidation of succinic acid to fumaric acid to bind to the enzyme and transfers the two electrons from FADH2 directly to the enzyme’s Fe³⁺.

Pydiflumetofen is a succinate dehydrogenase inhibitor and a fungicide.

From: Moreno C, et al. Cancers (Basel). 2020 Nov 3;12(11):3237.

As an important component of fungicides, succinate dehydrogenase inhibitors (SDHIs) inhibit the electron transfer between mitochondrial succinate and ubiquinone by completely or partially occupying the site of the substrate ubiquinone. Besides, they block the energy metabolism of pathogenic bacteria and inhibit their growth, thus, ultimately achieving bacterial inhibition.

Pydiflumetofen is a succinate dehydrogenase inhibitor and a fungicide. One study reported that Pydiflumetofen inhibited mycelial growth and conidial germination of Fusarium asiaticum by treatment for 3 days in the concentration range of 0-4 μg/mL. In addition, it suppresses mycelial growth with the EC₅₀ values of 0.019-0.2084 μg/mL and suppresses conidium germination with the EC₅₀ values of 0.0583-0.4237 μg/mL. Also, Pydiflumetofen shows no positive or negative cross-resistance with Carbendazim/Phenamacril.

In conclusion, Pydiflumetofen is a potent succinate dehydrogenase inhibitor and a fungicide.

Reference:

[1] Hou Y P, et al. Crop Protection ,Volume 96,2017, Pages 237-244.
[2] Huang S, et al.  Curr Opin Plant Biol. 2013 Jun;16(3):344-9.