Serine3

Serine3, or Ser3, is a gene name used in several organisms to designate an enzyme involved in serine biosynthesis, most notably in the yeast Saccharomyces cerevisiae. The Ser3 protein is a cytosolic dehydrogenase that participates in the early steps of converting glycolytic intermediates into the amino acid serine, contributing to the cellular serine pool.

In Saccharomyces cerevisiae, serine biosynthesis proceeds from glyceraldehyde-3-phosphate and 3-phosphoglycerate, with Ser3 catalyzing one of the initial reactions that feed into downstream steps producing serine. Ser3 is part of a network of serine biosynthetic enzymes that includes other Ser proteins; together they support serine production under nutrient-limited conditions and when environmental serine is scarce. The enzyme shows functional redundancy with related pathways, so deletion of SER3 can reduce serine synthesis but is not always lethal, depending on the growth conditions and the presence of compensatory enzymes.

Evolutionarily, Ser3 belongs to a family of serine biosynthesis enzymes that shares homology with bacterial 3-phosphoglycerate dehydrogenases. This reflects a conserved strategy across life to link central carbon metabolism with amino acid production. Orthologs or functionally similar enzymes are described in other fungi and eukaryotes, illustrating diversification of serine metabolism beyond a single species.

See also: serine biosynthesis, Ser1, Ser2, Saccharomyces cerevisiae, amino acid metabolism. Notes: the exact activity and regulation of Ser3 can vary by organism and cellular context, and environmental conditions often influence its contribution to serine homeostasis.