Phosphatidylserine (abbreviated Ptd-L-Ser or PS) is a phospholipid and is a component of the cell membrane.It plays a key role in cell cycle signaling, specifically in relation to apoptosis. It is a key pathway for viruses to enter cells via apoptotic mimicry.Its exposure on the outer surface of a membrane marks the cell for destruction via apoptosis.

Introduction

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.

Uses

Phosphatidylserine is used for Alzheimer disease and normal age-related decline in memory and thinking skills. It is also used for athletic performance, ADHD, and many other purposes, but there is no good scientific evidence to support most of these uses.

Biosynthesis

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).Similar to bacteria, yeast can form phosphatidylserine in an identical pathway.

In mammals, phosphatidylserine is instead derived from phosphatidylethanolamine or phosphatidylcholine through one of two Ca2+-dependent head-group exchange reactions in the endoplasmic reticulum. Both reactions require a serine but product an ethanolamine or choline, respectively. These are promoted by phosphatidylserine synthase 1 (PSS1) or 2 (PSS2).Conversely, phosphatidylserine can also give rise to phosphatidylethanolamine and phosphatidylcholine, although in animals the pathway to generate phosphatidylcholine from phosphatidylserine only operates in the liver.