Biomaterial Database

Topography of ether phospholipid biosynthesis. 1989

D Hardeman, and H van den Bosch

Centre for Biomembranes and Lipid Enzymology, University of Utrecht, The Netherlands.

The enzyme, dihydroxyacetone-phosphate acyltransferase (DHAP-AT) is localized at the inner surface of the peroxisomal membrane but shows no latency. The product, i.e., acyl-DHAP, is the first lipidic intermediate in ether lipid biosynthesis that is converted by alkyldihydroxyacetone-phosphate synthase into alkyl-DHAP. This step and the reductions of acyl-DHAP and alkyl-DHAP to the glycerol 3-phosphate analogs can still take place in peroxisomes. The further conversions of these intermediates into ether-linked choline or ethanolamine glycerophospholipids or plasmalogens take place in the endoplasmic reticulum. In this paper we describe studies to localize acyl-DHAP in the transversal plane of the peroxisomal membrane. To enable these studies, the usually employed assay conditions for DHAP-AT were modified by omission of BSA and by lowering the temperature and the palmitoyl-CoA concentration. Using these modified conditions, we were able to label peroxisomes with endogenously generated acyl-DHAP, with retention of catalase within the peroxisomal membrane. Endogenously generated acyl-DHAP was rapidly extractable from the outer surface of peroxisomes with BSA at 0 degree C, suggesting that even at this temperature the product was transported very fast across the membrane. Trypsin treatment of peroxisomes did not affect this behaviour. Only after short incubation periods, an increase in the proportion of non-extractable acyl-DHAP was observed. In large unilamellar vesicles made from peroxisomal phospholipids no transmembrane movement of acyl-DHAP was found. Despite the apparently rapid transbilayer movement of acyl-DHAP in the presence of BSA, it could still serve as a substrate for the enzyme alkyl-DHAP synthase, which is also localized at the inner surface of the peroxisomal membrane. In addition it was shown that endogenously generated substrate is used at a higher efficiency compared to exogenously added acyl-DHAP, suggesting a close interaction of the two enzymes in the peroxisomal membrane.

UI	MeSH Term	Description	Entries
D007425	Intracellular Membranes	Thin structures that encapsulate subcellular structures or ORGANELLES in EUKARYOTIC CELLS. They include a variety of membranes associated with the CELL NUCLEUS; the MITOCHONDRIA; the GOLGI APPARATUS; the ENDOPLASMIC RETICULUM; LYSOSOMES; PLASTIDS; and VACUOLES.	Membranes, Intracellular,Intracellular Membrane,Membrane, Intracellular
D008099	Liver	A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.	Livers
D008244	Lysophosphatidylcholines	Derivatives of PHOSPHATIDYLCHOLINES obtained by their partial hydrolysis which removes one of the fatty acid moieties.	Lysolecithin,Lysolecithins,Lysophosphatidylcholine
D008563	Membrane Lipids	Lipids, predominantly phospholipids, cholesterol and small amounts of glycolipids found in membranes including cellular and intracellular membranes. These lipids may be arranged in bilayers in the membranes with integral proteins between the layers and peripheral proteins attached to the outside. Membrane lipids are required for active transport, several enzymatic activities and membrane formation.	Cell Membrane Lipid,Cell Membrane Lipids,Membrane Lipid,Lipid, Cell Membrane,Lipid, Membrane,Lipids, Cell Membrane,Lipids, Membrane,Membrane Lipid, Cell,Membrane Lipids, Cell
D008830	Microbodies	Electron-dense cytoplasmic particles bounded by a single membrane, such as PEROXISOMES; GLYOXYSOMES; and glycosomes.	Glycosomes,Glycosome,Microbody
D010171	Palmitoyl Coenzyme A	A fatty acid coenzyme derivative which plays a key role in fatty acid oxidation and biosynthesis.	Palmitoyl CoA,Hexadecanoyl CoA,Palmityl CoA,CoA, Hexadecanoyl,CoA, Palmitoyl,CoA, Palmityl,Coenzyme A, Palmitoyl
D010742	Phospholipid Ethers	Phospholipids which have an alcohol moiety in ethereal linkage with a saturated or unsaturated aliphatic alcohol. They are usually derivatives of phosphoglycerols or phosphatidates. The other two alcohol groups of the glycerol backbone are usually in ester linkage. These compounds are widely distributed in animal tissues.	Ether Phosphatidates,Ether Phospholipids,Glycerol Phosphate Ethers,Glycerophosphate Ethers,1-Alkyl-2-Acylphosphatidates,1 Alkyl 2 Acylphosphatidates,Ethers, Glycerol Phosphate,Ethers, Glycerophosphate,Ethers, Phospholipid,Phosphate Ethers, Glycerol,Phosphatidates, Ether,Phospholipids, Ether
D002374	Catalase	An oxidoreductase that catalyzes the conversion of HYDROGEN PEROXIDE to water and oxygen. It is present in many animal cells. A deficiency of this enzyme results in ACATALASIA.	Catalase A,Catalase T,Manganese Catalase,Mn Catalase
D002793	Cholic Acids	The 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholanic acid family of bile acids in man, usually conjugated with glycine or taurine. They act as detergents to solubilize fats for intestinal absorption, are reabsorbed by the small intestine, and are used as cholagogues and choleretics.	Cholalic Acids,Acids, Cholalic,Acids, Cholic
D000217	Acyltransferases	Enzymes from the transferase class that catalyze the transfer of acyl groups from donor to acceptor, forming either esters or amides. (From Enzyme Nomenclature 1992) EC 2.3.	Acyltransferase