page_title: Sarcosine dehydrogenase
section_title: Mechanism
hierarchical_section_title: Sarcosine dehydrogenase / Mechanism
caption_attribution_description: English: Sarcosine to Glycine with THF
context_page_description: In enzymology, sarcosine dehydrogenase is a mitochondrial enzyme that catalyzes the chemical reaction N-demethylation of sarcosine to give glycine. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH group of donor with other acceptors. The systematic name of this enzyme class is sarcosine:acceptor oxidoreductase. Other names in common use include sarcosine N-demethylase, monomethylglycine dehydrogenase, and sarcosine: oxidoreductase. Sarcosine dehydrogenase is closely related to dimethylglycine dehydrogenase, which catalyzes the demethylation reaction of dimethylglycine to sarcosine. Both sarcosine dehydrogenase and dimethylglycine dehydrogenase use FAD as a cofactor. Sarcosine dehydrogenase is linked by electron-transferring flavoprotein to the respiratory redox chain.
  The general chemical reaction catalyzed by sarcosine dehydrogenase is:
  sarcosine + acceptor + H₂O glycine + formaldehyde + reduced acceptor
context_section_description: Sarcosine dehydrogenase, with sarcosine as its substrate, follows Michaelis–Menten kinetics and has a Km of 0.5 mM and a Vmax of 16 mmol/hr/mg protein. The enzyme is inhibited competitively by methoxyacetic acid, which has a Ki of 0.26 mM 
  The exact mechanism of sarcosine dehydrogenase is not available. However, according to the overall net reaction discussed in Honova.E, et al. paper:
  Sarcosine + H₂O + O₂ → glycine + formaldehyde + H₂O₂
  the first step of the reaction might involve the transfer of a hydride on the N-methyl group of sarcosine onto FAD, allowing H₂O to attack the carbocation in order to form intermediate 1 (See figure 1). There is no deamination step. Instead, the demethylation of the N-methyl group on sarcosine occurs directly. The reduced FADH⁻ from the first step then is oxidized by O₂ to form H₂O₂.
  The demethylation of sarcosine catalyzed by sarcosine dehydrogenase can proceed with or without the presence of tetrahydrofolate. Under anaerobic condition and without tetrahydrofolate, however, a free formaldehyde is formed after the N-demethylation of sarcosine. The reaction with 1 mole of sarcosine and 1 mole of FAD, under this condition, yields 1 mole of glycine and 1 mole of formaldehyde (See figure 2 for mechanism).
  Under the presence of tetrahydrofolate, sarcosine dehydrogenase binds to tetrahydrofolate and convert tetrahydrofolate to 5,10-methylenetetrahydrofolate. Tetrahydrofolate here serves as a 1-carbon acceptor during the demethylation process (See figure 3 for mechanism).
caption: Figure 3: Sarcosine going to glycine reaction mechanism with tetrahydrofolate (THF) present.[7]
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