Phosphatidylserine

Phosphatidylserine is a phospholipid—more specifically a glycerophospholipid—which consists of two fatty acids attached in ester linkage to the first and second carbon of glycerol and serine attached through a phosphodiester linkage to the third carbon of the glycerol. Phosphatidylserine sourced from plants differs in fatty acid composition from that sourced from animals. It is commonly found in the inner (cytoplasmic) leaflet of biological membranes. It is almost entirely found in the inner monolayer of the membrane with only less than 10% of it in the outer monolayer. == Biosynthesis ==

Phosphatidylserine (PS) is the major acidic phospholipid class that accounts for 13–15% of the phospholipids in the human cerebral cortex. In the plasma membrane, PS is localized exclusively in the cytoplasmic leaflet where it forms part of protein docking sites necessary for the activation of several key signaling pathways. These include the Akt, protein kinase C (PKC) and Raf-1 signaling that is known to stimulate neuronal survival, neurite growth, and synaptogenesis. Modulation of the PS level in the plasma membrane of neurons has a significant impact on these signaling processes. ==Composition==

Phosphatidylserine is formed in bacteria (such as E. coli) through a displacement of cytidine monophosphate (CMP) through a nucleophilic attack by the hydroxyl functional group of serine. CMP is formed from CDP-diacylglycerol by PS synthase. Phosphatidylserine can eventually become phosphatidylethanolamine by the enzyme PS decarboxylase (forming carbon dioxide as a byproduct). == Functions ==

Cognitive function Supplementation with PS has been studied with mixed results; while some short-term research (such as a 2001 trial on soy-derived PS with measurements at 6 and 12 weeks) found no significant effect on cognitive performance in the elderly with age-associated memory impairment, the U.S. FDA has permitted qualified health claims (with enforcement discretion) stating that phosphatidylserine may reduce the risk of dementia and cognitive dysfunction in the elderly, though noting the evidence is very limited and preliminary. Apoptosis PS plays a crucial role in the process of apoptosis (programmed cell death). During apoptosis, PS translocates from the inner leaflet of the cell membrane to the outer leaflet, serving as a signal for phagocytic cells to engulf the dying cell. ==Dietary sources==

The average daily phosphatidylserine intake in a Western diet is estimated to be 130mg. Phosphatidylserine may be found in meat and fish. Only small amounts are found in dairy products and vegetables, with the exception of white beans and soy lecithin. Phosphatidylserine is found in soy lecithin at about 3% of total phospholipids. Table 1. Phosphatidylserine content in different foods. ==Supplementation==

Health claims A panel of the European Food Safety Authority concluded that a cause and effect relationship cannot be established between the consumption of phosphatidylserine and "memory and cognitive functioning in the elderly", "mental health/cognitive function" and "stress reduction and enhanced memory function". According to the FDA, there is a lack of scientific agreement amongst qualified experts that a relationship exists between phosphatidylserine and cognitive function. though the mechanism remains unclear. A 2020 review of three clinical trials found that phosphatidylserine is likely effective for enhancing cognitive function in older people with mild cognitive impairment. Some studies have suggested that whether the phosphatidylserine is plant- or animal-derived may have significance, with the FDA's statement applying specifically to soy-derived products. Safety Initially, phosphatidylserine supplements were derived from bovine cortex. However, due to the risk of potential transfer of infectious diseases such as bovine spongiform encephalopathy (or "mad cow disease"), soy-derived supplements became an alternative. Some manufacturers of phosphatidylserine use sunflower lecithin instead of soy lecithin as a source of raw material production. == References ==