Ceramide synthesis wikipedia
In case of glycosphingolipids, exohydrolases, acting at acidic pH optima, cause the stepwise release of monosaccharide units from the end of the oligosaccharide chains one after the other leading to the generation of ceramide whereas sphingomyelin is converted to ceramide by acid sphingomyelinase.
Galactosylceramides have not been found in plants. The corresponding defect for galactocerebrosides is Krabbe disease.
Monoglycosyl and oligoglycosylceramides synthesis a mono or polysaccharide bonded glycosidically to the terminal Digital direct synthesis group of ceramide are defined as cerebrosides. Ceramide is subsequently transported to the Golgi by either vesicular trafficking or the ceramide transfer protein CERT.
These hydrogen bonds within the cerebrosides result in the molecules having a high transition temperature and compact alignment. Sphingomyelin hydrolysis Hydrolysis of sphingomyelin is catalyzed by the enzyme sphingomyelinase.
Ceramide accumulation has been found following treatment of cells with a number of apoptotic agents including ionizing radiation,   UV light,  TNF-alpha and chemotherapeutic agents.
Cerebrosides containing a sulfuric ester sulfate group, known as sulfatides, also occur in the myelin sheath of nerves. All mammalian CerS, aside from CerS1, contain a Hox -like domain shared by synthesis factors important in development, although the first 15 amino acids of this domain are missing in CerS, indicating that this domain likely does not function as a genuine transcription factor.
The final reaction to produce ceramide is catalyzed by dihydroceramide desaturase. The word ceramide comes from the Latin cera wax and amide. Several studies have attempted to define further the specific role of ceramide in the events of cell death and some evidence suggests ceramide functions upstream of the mitochondria in inducing apoptosis.
Synthesis[ edit ] The biosynthesis of monoglycosylceramides requires a direct transfer of the carbohydrate moiety from a sugar-nucleotide, such as uridine 5-diphosphate UDP -galactose, or UDP-glucose to the ceramide unit. Because of its apoptosis-inducing effects in cancer cells, ceramide has been termed the "tumor suppressor lipid".
It is functionally and structurally distinct from other CerS and is found in an entirely different branch of the phylogenetic tree. Ceramide accumulation has been found following treatment of cells with a number of apoptotic agents including ionizing radiation  UV light TNF-alpha and chemotherapeutic agents.
Granule cells also showed a 6 times increased rate of apoptosis. However, owing to the conflicting and variable nature of studies into the role of ceramide in apoptosis, the mechanism by which this lipid regulates apoptosis remains elusive.
The salvage pathway re-utilizes long-chain sphingoid bases to form ceramide through the action of ceramide synthase.
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