Schematic of glycine and serine metabolism. In the cytoplasm, the enzymes PHGDH, PSAT, and PSPH convert 3-phosphoglycerate into serine. SHMT1 can convert serine into glycine, while generating CH2-THF in the 1-carbon cycle. Products from the 1-carbon cycle are used for purine and methionine synthesis. In the mitochondria, SHMT2 can convert serine into glycine, while generating CH2-THF in the 1-carbon cycle. The glycine cleavage system, consisting of the enzymes GLDC, AMT, and DLD, also generates CH 2 -THF for the 1-carbon cycle. Abbreviations GLY (glycine), SER (serine), 3PG (3-phosphoglycerate), 3PHP (3-phosphohydroxypyruvate), pSER (phosphoserine), H-am (H-protein aminomethylated), H-ox (H-protein oxidized), H-red (H-protein reduced), THF (tetrahydrofolate), CH 2 -THF (5,10-methylene tetrafhydrofolate)
