Figure 2

Major folate-dependent reactions of one-carbon metabolism. The gene names are for E. coli (except for sarcosine dehydrogenase). Note that the formation of 5-formyl-THF from 5,10-methenyl-THF occurs via a second catalytic activity of serine hydroxymethyltransferase (glyA), and that 5-formyl-THF is reconverted to 5,10-methenyl-THF by 5-formyl-THF cycloligase (ygfA). For simplicity, THF is not shown as a participant in most reactions in which it is consumed or released. GCV, glycine cleavage complex, comprising the products of the gcvT, gcvH, gcvP, and lpd genes; SDH, sarcosine dehydrogenase (not present in E. coli).