 Glucose 1-phosphate

Glucose 1-phosphate is a glucose-derived phosphate ester with phosphate attached through the oxygen at carbon1, the anomeric carbon in the cyclic sugar. The attachment position is part of its identity: glucose-6-phosphate has the phosphate at a different carbon. An explicit example is α-D-glucose 1-phosphate, whose ChEBI record specifies the α configuration at the anomeric center.^[ref]

The neutral acid representation in that record has molecular formula ${\mathrm{C}}_6{\mathrm{H}}_{13}{\mathrm{O}}_9\mathrm{P}$. This counts one phosphorus atom per sugar unit; proton loss changes charge and hydrogen count without moving the phosphate attachment. Distinguishing the anomer, attachment position and protonation state is more informative than reporting only total phosphorus.^[ref]

A biological example is production of α-D-glucose 1-phosphate by glycogen phosphorylase. The enzyme transfers a terminal glucosyl unit from a suitable glycogen chain to inorganic phosphate; this is phosphorolysis, rather than simple release of free glucose by hydrolysis.^[ref]

For an original assay-accounting example, a reaction extent of $2\mu \mathrm{mol}$ for this one-unit cleavage consumes $2\mu \mathrm{mol}$ inorganic phosphate and forms $2\mu \mathrm{mol}$ glucose 1-phosphate. It transfers phosphorus between free and sugar-bound pools without changing the total phosphorus in a closed sample. A total-phosphorus assay could therefore remain constant while a molecule-specific assay detects product formation. The stated extent is a bookkeeping example, not a predicted yield near glycogen branch points or at chemical equilibrium.