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Mannosyl-di-(inositolphosphoryl)-ceramide

About the structure and biological function of M(IP)2C

Mannosyl-di-(inositolphosphoryl)-ceramides (M(IP)2C) are a type of glycophosphosphingolipids, a subclass of phosphosphingolipids. Their structure consists of a ceramide base bound to two linked phosphorylinositol molecules of which one is mannosylated. The ceramide base contains two hydrocarbon chains, the long-chain base and a fatty acid. M(IP)2C lipids are mainly found in fungi. On a subcellular level, they are enriched in the cell membrane.

Little is known about the biological function of mannosyl-di-(inositolphosphoryl)-ceramides but they are important components of biological membranes of fungi. Together with MIPC, they constitute the major sphingolipids in yeasts. As M(IP)2C lipids are not produced in mammals, targeting their synthesis is a strategy for novel antifungal drugs. Further, M(IP)2C ceramides interact with plant defensins, small peptides produced by plants that possess antifungal activity.

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Mannosyl-inositolphosphoryl-ceramide

About the structure and biological function of MIPC

Mannosyl-inositolphosphoryl-ceramides (MIPC) are a type of glycophosphosphingolipids, a subclass of phosphosphingolipids. Their structure consists of a ceramide base bound to a mannosylated phosphorylinositol molecule. The ceramide base contains two hydrocarbon chains, the long-chain base and a fatty acid. MIPC lipids are mainly found in fungi. On a subcellular level, they are enriched in the cell membrane.

Mannosyl-inositolphosphoryl-ceramides are important components of biological membranes of fungi. Together with M(IP)2C, they constitute the major sphingolipids in yeasts, where they have multiple functions related to maintenance of cell morphology and are required for the localization of cell membrane proteins. Depending on the immune status of the host, MIPC ceramides of the pathogenic yeast candida albicans indirectly cause immune system disorder and persistent fungal disease.

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Inositolphosphoryl-ceramide

About the structure and biological function of IPC

Inositolphosphoryl-ceramides (IPC) are a type of phosphosphingolipids, a class of sphingolipids. Their structure consists of a ceramide base bound to a phosphorylinositol molecule. The ceramide base contains two hydrocarbon chains, the long-chain base and a fatty acid. IPC lipids are found in many eukaryotes such as fungi and plants but not mammals. On a subcellular level, they are enriched in the cell membrane.

Inositolphosphoryl-ceramides are substantial components of biological membranes in yeast. In lipid rafts of the cell membrane, IPC lipids interact with membrane proteins with signaling functions – a role similar to those of sphingomeylins in animals. IPC ceramides are also the precursor for further complex glycophosphosphingolipids. Further, the biosynthesis of IPC lipids reduces the pool of intracellular ceramide and thus inhibits programmed cell death.

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Ergosteryl ester

About the structure and biological function of EE

Ergosteryl esters are a type of sterol lipids. Their structure consists of ergosterol where an ester bond is formed between the hydroxyl group of the steroid structure and a fatty acid. The fatty acid can be of variable length, hydroxylated, and contain double bonds. Ergosteryl esters are found in fungi and also some unicellular eukaryotes. On a subcellular level, they are enriched in cellular lipid droplets.

The biological function of ergosteryl esters revolves mainly around ergosterol storage in yeast. During growth retarding conditions but also after fungal death, ergosterol is esterified and stored in cellular lipid droplets. Once esterified, the fatty acids of the ergosteryl esters are not scavenged even during starvation conditions. Further, some ergosteryl esters also show strong growth inhibitory activity against dairy and cosmetic spoilage bacteria.

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Ergosterol

About the structure and biological function of Erg

Ergosterol is a type of sterol lipid. Similar to cholesterol, the structure of ergosterol consists of four linked hydrocarbon rings, the steroid structure. A hydrocarbon tail is linked to one end of the steroid, a hydroxyl group linked to the other end. It contains no fatty acids. Ergosterol is the major sterol lipid in fungi and also some unicellular eukaryotes. On a subcellular level, it is enriched in the cell membrane.

Ergosterol serves an important structural role in the cell membrane of fungi and also forms lipid rafts – similar to cholesterol in animal cells. Under conditions of stress, the sterol concentration of the cell membrane can change rapidly. It also has multiple functions in growth regulation and is a precursor to vitamin D2. Further, a range of antifungal drugs targets ergosterol by either binding to it in the cell membrane to cause cellular leakage, or by preventing ergosterol synthesis.

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CDP-diacylglycerol

About the structure and biological function of CDP-DAG

CDP-DAG lipids are a type of CDP-glycerols, a class of glycerophospholipids. Their structure consists of a glycerol backbone linked to two fatty acids and a cytidine diphosphate molecule (CDP). The fatty acids can be of various lengths, hydroxylated, and contain double bonds. CDP-DAG lipids are found in eukaryotic and prokaryotic cells. On a subcellular level, they are enriched in the endoplasmic reticulum and in mitochondria.

CDP-DAG lipids occupy a branch point in the biosynthesis of complex glycerolipids. The distinct end-products depend on the subcellular location of synthesis. For example, CDP-DAGs are used for cardiolipin biosynthesis in mitochondria and for phosphatidylinositol and phosphatidylglycerol synthesis in the endoplasmic reticulum. Thus, CDP-DAG lipids also have a key role in regulation of phosphatidylinositol signal transduction. Further, they are linked to lipid droplet size in adipocytes.

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