Serine

An amino acid for phospholipid synthesis (phosphatidylserine), myelin synthesis and as a neurotransmitter precursor (D-serine at NMDA receptors).

What serine does in the body

The body can make serine itself from an intermediate of sugar breakdown (3-phosphoglycerate); in the brain this is done mainly by the support cells. Serine is the starting point of several pathways: with folate and vitamin B6 it becomes glycine and in the process releases a carbon unit needed for building genetic material and for methylation. Together with a fatty acid it forms the sphingolipids, which include sphingomyelin, a main component of the myelin sheaths around nerve fibres. Phosphatidylserine sits on the inner side of cell membranes; if it appears on the outside, this is the signal for scavenger cells to clear away a dying cell. With homocysteine and vitamin B6, serine is involved in the pathway to cysteine. In the brain part of it is converted into D-serine, which acts at the NMDA receptor as a partner of glutamate.

Low serine – what happens in the body?

When little serine is available, the enzyme that makes sphingolipids falls back on alanine or glycine instead. This produces deoxysphingolipids, which cannot be broken down further and damage nerve cells; this process has been described in an inherited form of nerve damage and has also been observed in studies in nerve damage caused by diabetes. At the same time, less glycine and fewer carbon units for folate metabolism are produced. Rare inherited disorders of serine production impair the development of the nervous system and are associated with seizures.

High serine – what does it mean?

A moderately raised value usually has no known consequence of its own. It can show that less serine is being processed further into glycine and cysteine – these steps need folate and vitamin B6 –, or that more serine was taken in with protein-rich meals. For the brain, what matters most is the D-serine formed there, the amount of which the blood value does not reflect directly.

The interpretation is given in your report.