Lserine

L-serine is an α-amino acid used in the biosynthesis of proteins and a variety of other biomolecules. It occurs in the L-configuration in proteins and is one of the 20 standard amino acids. L-serine has a polar, uncharged side chain (a hydroxymethyl group) and participates in many metabolic pathways beyond its role as a protein building block.

In humans, L-serine can be synthesized endogenously and is considered nonessential, though it is conditionally essential under certain conditions such as rapid growth or metabolic stress. The primary endogenous source is the serine biosynthesis pathway, derived from the glycolytic intermediate 3-phosphoglycerate. The sequence involves three enzymes: 3-phosphoglycerate dehydrogenase, phosphoserine aminotransferase, and phosphoserine phosphatase, yielding free L-serine. L-serine is a key donor of one-carbon units through its conversion to glycine via serine hydroxymethyltransferase, linking it to folate-mediated one-carbon metabolism. It also serves as a precursor for other important compounds, including cysteine, phosphatidylserine, and sphingolipids.

Dietary sources of L-serine include meat, fish, eggs, dairy products, legumes, and cereals. In normal physiology, dietary intake plus endogenous production generally meet metabolic needs, but deficiencies can occur in rare genetic disorders affecting serine biosynthesis, such as PHGDH, PSAT1, and PSPH deficiencies. These serine deficiency disorders can cause developmental and neurological problems; management in affected individuals may involve dietary L-serine supplementation under medical supervision. Research continues into potential therapeutic roles for L-serine in certain neuropathies and metabolic conditions.

See also: D-serine, serine biosynthesis, serine hydroxymethyltransferase.