Serine

Serine is also a precursor for phosphatidylserine, sphingolipids, and D-serine (important NMDA receptor co-agonist). Serine can be synthesized from 3-phosphoglycerate (glycolysis intermediate) via the phosphorylated pathway, or from glycine via SHMT. Cancer cells often have increased serine synthesis and utilization due to high demand for nucleotides and methylation.

Metabolic Connections

Serine connects to 10 other pathways.

Detoxification

CBS

Serine is used by CBS as substrate, combined with homocysteine

Cystathionine beta-synthase - enzyme directing homocysteine toward glutathione production via the transsulfuration pathway.

Metabolites

Cystathionine

Serine contributes to cystathionine formation

Intermediate in transsulfuration pathway; formed from homocysteine and serine by CBS enzyme.

Cystathionine

Serine is combined with homocysteine by CBS to form cystathionine

Intermediate in transsulfuration pathway; formed from homocysteine and serine by CBS enzyme.

B Vitamins

Folate

Serine-glycine interconversion transfers one-carbon units to/from THF

Vitamin B9 - essential for DNA synthesis, methylation, and cell division. Critical during pregnancy for neural tube development.

Amino Acids

Glycine

Serine can be converted to glycine by SHMT

Simplest amino acid with diverse roles - glutathione component, collagen synthesis, neurotransmission, and methylation.

Glycine

Glycine and serine are interconverted by SHMT

Simplest amino acid with diverse roles - glutathione component, collagen synthesis, neurotransmission, and methylation.

Metabolic Cycles

Glycolysis

Serine can be synthesized from the glycolysis intermediate 3-phosphoglycerate

Ten-step pathway breaking down glucose to pyruvate, producing ATP and NADH. Occurs in cytoplasm without oxygen.

Methylation

Homocysteine

Serine combines with homocysteine via CBS

Sulfur-containing amino acid at the crossroads of methylation. Elevated levels indicate impaired methylation or B-vitamin deficiency.

Enzymes

SHMT (Serine Hydroxymethyltransferase)

SHMT interconverts serine and glycine while transferring one-carbon units

Enzyme interconverting serine and glycine; major source of one-carbon units for folate pool; B6 dependent.

SHMT (Serine Hydroxymethyltransferase)

SHMT converts serine to glycine

Enzyme interconverting serine and glycine; major source of one-carbon units for folate pool; B6 dependent.