In nucleotide sugar metabolism
a group of biochemicals
known as nucleotide sugars
act as donors for sugar residues in the glycosylation
reactions that produce polysaccharides
. They are substrates for glycosyltransferases
. The nucleotide sugars are also intermediates in nucleotide sugar interconversions that produce some of the activated sugars needed for glycosylation reactions. Since most glycosylation takes place in the endoplasmic reticulum
and golgi apparatus
, there are a large family of nucleotide sugar transporters
that allow nucleotide sugars to move from the cytoplasm
, where they are produced, into the organelles where they are consumed.
Nucleotide sugar metabolism is particularly well-studied in bacterial pathogens, such as E. coli and Mycobacterium tuberculosis, since these molecules are required for the synthesis of glycoconjugates on the surfaces of these organisms. These glycoconjugates are virulence factors and components of the bacterial cell wall. These pathways are also studied in plants, but here the enzymes involved are less well understood.