Folate metabolism compartmentation

Figure 8 Extended folate metabolism, including compartmentation. MTHFR, methylenetetrahydrofolate reductase SHMT, serine hydroxymethyltransferase BHMT, betaine homocysteine methyltransferase, MAT, methionine adenosyltransferase SAH-hydrolase, S-adenosylhomocysteine hydrolase MT, methyltransferase CBS, cystathionine /i-synthase SAM, S-adenosylmethionine SAH, S-aden-osylhomocysteine THF, tetrahydrofolate and 5-MeTHF, 5-methyltetrahydrofolate. (Reproduced from Van der Put etal. (2001) Folate, homocysteine and neural tube defects An overview. Experimental Biology and Medicine 226 243-270.)...

Folate metabolism is not limited to the cytoplasmic compartment. Most of the folate in tissues is found in the mitochondrion and cytosol (Horne et al. 1997). Individual folate-dependent pathways are compartmentalized within organelles. The cytoplasmic and mitochondrial compartments each possess a parallel array of enzymes catalysing the interconversion of folate coenzymes that carry one-carbon units. The mitochondrial folate metabolism favours incorporation of one-carbon groups from serine and release of formate, while the cytoplasmic metabolism favours incorporation of one-carbon units from formate with purine and thymidine synthesis and homocysteine remethylation. 

APPLING, D.R., Compartmentation of folate-mediated one-carbon metabolism in eukaryotes, FASEB J., 1991, 5, 2645-2651. 

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