Glycerophosphoserines (GP03)

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Contents

Basics

Phosphatidylserine is known chemically as 1,2-diacyl-sn-glycerol-(3)-L-phosphoserine. It is abbreviated as Ptd Ser, Acyl2 Gro PSer and PS. Phosphatidylserine was first isolated from brain lipids called cephalins.

Structure

Phosphatidylserine
Phosphatidylserine

Formula: C8H12NO10PR2

LIPID MAPS Glycerophospholipid classes and subclasses

Phosphatidylserine is made up of a glycerophosphate skeleton linked to two fatty acid molecules and the amino acid L-serine. It is an amphiphilic molecule because it is made up of the lipophilic fatty acid tails on one side and the hydrophilic head group containing phosphate and serine on the other side of the molecule.

Location

Phosphatidylserine is located in the internal layers of biologic membranes, facing the cytoplasm with its polar head group. In animal tissues, phosphatidylserine is formed from phosphatidylethanolamine by exchange of the ethanolamine head for L-serine.

Natural sources

Phosphatidylserine

Nomenclature

Synonyms

  • Phosphatidylserine
  • Phosphatidyl-L-serine
  • 1,2-Diacyl-sn-glycerol 3-phospho-L-serine
  • O3-Phosphatidyl-L-serine
  • 3-O-sn-Phosphatidyl-L-serine

IUPAC

Glycerophospholipids and subclasses

Biophysical properties

Biology / biochemistry

Biochemical synthesis

PS is formed by the condensation of serine with a phosphatidic acid (PA) moiety, where in mammalian cells phosphatidylcholine or phosphatidylethanolamine serve as the phosphatidyl donors catalyzed by PS-Synthases (PSS I/II) (Fig. 25_2). Nascent PS is subsequently decarboxylated to form PE, and this reaction is catalyzed by PS-Decarboxylase (PSD). This pathway is found in mammalian cells but there are some tight restrictions on specific elements of the pathway. The methylation of PE only occurs quantitatively significant in the liver.

Figure 25_2. Synthesis and catabolism of phosphatidylserine to phosphatidyethanolamine
Figure 25_2. Synthesis and catabolism of phosphatidylserine to phosphatidyethanolamine


PS synthase

In the last years the endoplasmic reticulum and a novel ER-related fraction have been identified as the principal intracellular localization sites of PS-Synthase. The ER-related fraction is tightly associated with the mitochondria and currently referred to as the mitochondria-associated membrane (MAM) compartment. The MAM-compartment can be isolated as a distinct cellular fraction and has significant enrichment in PS-Synthase activity when compared with the total microsomal membrane population. Both morphological and biochemical studies have suggested that the zones of association between the MAM and the mitochondria may also be sites of contact between the outer and inner mitochondrial membrane (Fig. 26_2).

Figure 26_2. Synthesis and catabolism of phosphatidylserine to phosphatidyethanolamine
Figure 26_2. Synthesis and catabolism of phosphatidylserine to phosphatidyethanolamine

PS Decarboxylase

PS-Decarboxylase was found to be a constituent of the inner mitochondrial membrane and there is a preference for the movement of newly synthesized PS to mitochondria. The PE generated in mitochondria does not only serve as a structural lipid in the mitochondria but is preferentially utilized as a substrate for the methyltransferase reaction to form PC and additionally is exported from mitochondria to function in the biogenesis of other organelles. The mechanism by which mitochondrial PE is transported to the plasma membrane is not known, but the process is energy dependent and insensitive to the Golgi disrupting toxin brefeldin A. The results with brefeldin A indicate that the route followed by PE is likely to bypass the Golgi apparatus.

Metabolism

Enzymes/gene lists

Associated biological processes

Technology

Analysis methods

Chemical synthesis

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