GlcCer, GalCer , geramide, glukosyl, galaktosyl , GBA1 ja GBA2 transglykosyloivat ja myös transgalaktosyloivat , GlcChol, GalChol

 AIEMPI tekstini:

Synteesi KERAMIDISTA kohti glykosfingolipidejä.KERAMIDI (Cer) syntyy endoplasmisessa retikulumissa ja se kulkeutuu Golgin laitteeseen.. Keramidia purkautuu myös sfingolipidien kataboliasta ja käytetään uudestaan.

GlcCer, glucosylceramide, glukosyylikeramidi

GlcCer syntaasientsyymi lisää glukoosin beta-sidoksella keramidin OH- ryhmään 1- asemassa.Glukosyylikeramidiin tapahtuva jatkosyntetisoiminen tapahtuu sen jälkeen kun karakterisoimattoman flippaasi-entsyymin avulla on tapahtunut vaihde Golgin laitteen ontelon puolelle.

http://link.springer.com/chapter/10.1007%2F978-4-431-67877-9_1#page-1

GalCer, galactosylceramide, galaktosyylikeramidi muodostusta voi myös joskus tapahtua keramidista. Tämä tapahtuu endoplasmisen retikulumin ontelon puolella, vaikkakin galaktosyylikeramidien synteesitietä tapahtuu vain hyvin rajoitetusti.

http://link.springer.com/chapter/10.1007%2F978-4-431-67877-9_8#page-1

PÄIVITYSTÄ GlcCer ja GalCer synteesiasiaan  11.5. 2023

On uudempaa tietoa on GlcCer ja GalCer muodostumisesta aineenvaihdunnassa vuodelta 2020

https://www.jbc.org/article/S0021-9258(17)48548-6/fulltext

β-Glucocerebrosidase (GBA) hydrolyzes glucosylceramide (GlcCer) to generate ceramide. Previously, we demonstrated that lysosomal GBA1 and nonlysosomal GBA2 possess not only GlcCer hydrolase activity, but also transglucosylation activity to transfer the glucose residue from GlcCer to cholesterol to form β-cholesterylglucoside (β-GlcChol) in vitro. β-GlcChol is a member of sterylglycosides present in diverse species. How GBA1 and GBA2 mediate β-GlcChol metabolism in the brain is unknown. Here, we purified and characterized sterylglycosides from rodent and fish brains. Although glucose is thought to be the sole carbohydrate component of sterylglycosides in vertebrates, structural analysis of rat brain sterylglycosides revealed the presence of galactosylated cholesterol (β-GalChol), in addition to β-GlcChol. Analyses of brain tissues from GBA2-deficient mice and GBA1- and/or GBA2-deficient Japanese rice fish (Oryzias latipes) revealed that GBA1 and GBA2 are responsible for β-GlcChol degradation and formation, respectively, and that both GBA1 and GBA2 are responsible for β-GalChol formation. Liquid chromatography–tandem MS revealed that β-GlcChol and β-GalChol are present throughout development from embryo to adult in the mouse brain.

We found that β-GalChol expression depends on galactosylceramide (GalCer), and developmental onset of β-GalChol biosynthesis appeared to be during myelination. We also found that β-GlcChol and β-GalChol are secreted from neurons and glial cells in association with exosomes.

In vitro enzyme assays confirmed that GBA1 and GBA2 have transgalactosylation activity to transfer the galactose residue from GalCer to cholesterol to form β-GalChol. This is the first report of the existence of β-GalChol in vertebrates and how β-GlcChol and β-GalChol are formed in the brain.