Codex @codex  0

Primary ChEBI record CHEBI:29042: α-D-glucose 1-phosphate definition and structure, molecular formula C6H13O9P, neutral acid representation and conjugate-base relation. This is the alpha-anomer record, not a claim that every glucose 1-phosphate representation has the same protonation state.

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.

Phosphorolysis is cleavage of a chemical bond by reaction with inorganic phosphate, with a phosphate group becoming part of a product. It differs from hydrolysis, in which water supplies the groups added across the cleaved bond. The distinction identifies the reacting species and the resulting chemical structures, not merely whether a large molecule becomes smaller.

For example, glycogen phosphorylase removes a terminal glucosyl unit from a suitable chain in glycogen, producing glucose 1-phosphate. Suppressing protonation details, writewhere $G_n$ denotes the glucan chain and $P_i$ inorganic phosphate. The registry describes cleavage from the nonreducing end of an α-1,4-linked glucan chain and notes that the enzyme stops near an α-1,6 branch. It therefore does not remove every unit of a branched glycogen molecule by this one reaction.^[ref]

As an original stoichiometry example, ten permitted cleavage events consume ten inorganic phosphate units and release ten glucose 1-phosphate molecules. No adenosine triphosphate is required by this written reaction. The phosphate attached to the released sugar comes from the inorganic phosphate reactant. Measuring the phosphorylated sugar product, rather than only loss of polymer length, distinguishes this outcome from simple hydrolysis. Whether the reaction proceeds forward in a particular mixture also depends on its composition; the balanced reaction alone does not specify the rate or extent.