Sugar branches & glycans
Monosaccharide entry routes and the activated-sugar chemistry used to construct, remodel and recover extracellular-matrix carbohydrates.
Fructose and galactose do not enter central metabolism through one universal gate. Their first reactions depend on tissue enzyme expression and create distinct phosphorylated intermediates before carbon reaches the glucose-phosphate or triose-phosphate network.
Glycosaminoglycans are not fuel polymers. Their repeating disaccharides are assembled, modified and sulfated through activated donors in the secretory system, then degraded through ordered lysosomal steps. Missing one step can block turnover even when neighboring hydrolases remain active.
The map keeps monosaccharide catabolism and glycan assembly in one territory to show shared activated-sugar chemistry without implying that extracellular-matrix chains feed directly into glycolysis.
Ideas to carry into the map
- Different dietary sugars have distinct entry chemistry.
- Activated sugars support biosynthesis as well as catabolism.
- Lysosomal glycan turnover is ordered and compartment-specific.
Pathways in this field note
Tissue-contextual routes that phosphorylate and split fructose before its carbon joins central carbohydrate metabolism.
The Leloir-route chemistry that converts galactose-derived carbon into glucose-phosphate intermediates.
Biosynthesis and turnover of sulfated and non-sulfated glycosaminoglycan chains across secretory and lysosomal compartments.
Stepwise lysosomal recovery of monosaccharides from complex oligosaccharides.