Glucosylceramide
= Glucosylceramide
A \b[glucosylceramide] is a <glycosphingolipid> with a single <glucose> residue as its carbohydrate headgroup, linked to a <ceramide>. The name identifies a structural class: the long-chain base and <fatty acid> portions can vary. Consequently, “glucosylceramide” does not generally specify one molecular formula or one exact <molar mass>.<Glucosylceramide in ChEBI>[CHEBI:36500, definition and variable-substituent structure]{ref}
The D-glucosyl-N-acylsphingosine subclass illustrates the connectivity. Its glucose group substitutes the1-hydroxyl of <sphingosine>, while an acyl group substitutes the2-amino group to form the <ceramide> portion. The <glycosidic bond> attaches the sugar; the <amide bond> attaches the fatty-acyl component. These are chemically different connections.<Glucosylceramide in ChEBI>[CHEBI:18368, definition and structure]{ref}
For a counting example,2micromoles of glucosylceramide molecules contain2micromoles of glucose-derived residues and therefore12micromoles of carbon atoms in those residues. This does not count the carbon in the variable <ceramide> portions or determine the sample mass.
The accepted <ceramide glucosyltransferase> reaction uses <UDP-glucose> as the glucose donor and releases UDP while forming the glucosylated lipid. Thus biosynthesis uses an activated donor; the structural description “ceramide plus glucose” is not an assertion that free glucose spontaneously condenses onto the lipid in a cell.<Enzyme Nomenclature by the IUBMB>[EC2.4.1.80, Reaction and Comments]{ref}