Different variants of D-glucose with their names and KEGG accession codes. The α – and β-D-glucopyranose forms account for 37% and 63% respectively of the equilibrium mixture in aqueous solution. The open form, absent from KEGG, is present in small amounts. The D-glucofuranose forms (five-membered rings) are not shown, as they are only present in insignificant amounts. The fact that C00031 represents the equilibrium mixture of C00221 and C00263 causes a problem in consistency of database management of these compounds.