In Vivo Rate of Formaldehyde Condensation with Tetrahydrofolate

Abstract

Formaldehyde is a highly reactive compound that participates in multiple spontaneous reactions, but these are mostly deleterious and damage cellular components. In contrast, the spontaneous condensation of formaldehyde with tetrahydrofolate (THF) has been proposed to contribute to the assimilation of this intermediate during growth on C1 carbon sources such as methanol. However, the in vivo rate of this condensation reaction is unknown and its possible contribution to growth remains elusive. Here, we used microbial platforms to assess the rate of this condensation in the cellular environment. We constructed Escherichia coli strains lacking the enzymes that naturally produce 5,10-methylene-THF. These strains were able to grow on minimal medium only when equipped with a sarcosine (N-methyl-glycine) oxidation pathway that sustained a high cellular concentration of formaldehyde, which spontaneously reacts with THF to produce 5,10-methylene-THF. We used flux balance analysis to derive the rate of the spontaneous condensation from the observed growth rate. According to this, we calculated that a microorganism obtaining its entire biomass via the spontaneous condensation of formaldehyde with THF would have a doubling time of more than three weeks. Hence, this spontaneous reaction is unlikely to serve as an effective route for formaldehyde assimilation.

The toxic side of one-carbon metabolism and epigenetics

“…The one-carbon flux implies the movement of reactive formaldehyde, which can affect several cellular structures. Interestingly, it was described that free formaldehyde can spontaneously condensate with THF, producing 5,10-CH2-THF [ 74 , 75 ]. This reaction might alter the endogenous level of 5,10-CH2-THF, affecting multiple biochemical reactions that depend on this THF derivative.…”

Peer Review #1 of "Investigation of microbial community interactions between Lake Washington methanotrophs using ­­­­­­­genome-scale metabolic modeling (v0.1)"

“…Genome annotations of methanotrophs indicate that formaldehyde assimilation can happen through the oxidative Pentose Phosphate Pathway as well as the formaldehyde/formate dehydrogenases and the tetrahydrofolate-associated pathways (Cai et al 2016;Khmelenina et al 2018). However, there have been extensive evidences that the Ribulose Monophosphate (RuMP) cycle is the major route for formaldehyde assimilation (Fu et al 2017;He et al 2020;Peyraud et PeerJ reviewing PDF | (2020:02:45973:2:0:NEW 28 May 2020)…”

“…2011). Also, multiple studies indicate that formaldehyde assimilation through the Serine cycle is insignificant (de la Torre et al 2015;Fu et al 2017;He et al 2020). Based on transcriptomic data and metabolic flux measurements(de la Torre et al 2015; Fu et al 2017), we restricted the distribution of formaldehyde assimilation between the RuMP cycle and the tetrahydrofolateassociated pathways.…”

Formaldehyde regulates tetrahydrofolate stability and thymidylate synthase catalysis

“…1). 11,12 Given the exposure of cells to HCHO from exogenous sources and via intracellular enzymatic demethylation reactions, [13][14][15] it seems Fig. 1 Mechanisms of folic acid-and glutathione-mediated HCHO metabolism.…”