D-Glucose 1-phosphate formation by cyanogen-induced phosphorylation of D-glucose. Synthesis, mechanism, and application to other reducing sugars
D-Glucose in dilute aqueous solution (pH 6·7–8·8) in the presence of orthophosphate and cyanogen is phosphorylated to produce α-D-glucopyranose 1-phosphate (yield 8–20%), β-D-glucopyranose 1-phosphate (2–5%), and a phosphorylated disaccharide (3–34%). The products were identified by paper chromatography and electrophoresis and by hydrolytic studies. The first-order rate constants for hydrolysis of α- and β-glucopyranose 1-phosphate in 1·16M-perchloric acid at 25° are 4·14 × 10–5 s–1, respectively. α-D-Glucose 1-phosphate (Cori ester) was further identified by a highly specific enzymic assay.
The cyanogen-induced phosphorylation is a general reaction for reducing sugars; non-reducing sugars are inert. Thus, phosphorylation is also successful with the monosaccharides D-arabinose, D-ribose, D-xylose, D-galactose, D-mannose, D-fructose, D-glucosamine, N-aceyl-D-glucosamine, and with the disaccharides maltose, melibiose, cellobiose, and lactose, but fails with glycerol, sucrose, and trehalose.
In the case of D-arabinose, the products are D-arabinopyranose 1-phosphate and D-arabinofuranose 1-phosphate, obtained in 3–5% and 0·5–1·5% yield, respectively.
Evidence for the mechanism of cyanogen-induced phosphorylation was obtained by studying the hydrolysis of cyanogen and orthophosphate in H218O. The observed rapid uptake of 18O into the orthophosphate, without isotopic dilution of the water, indicates initial formation of a cyanogen–phosphate adduct [CN–CN + HPO42–→ NC–C(NH)–O·PO32–] which then undergoes hydrolysis to produce 18O-labelled orthophosphate [NC–C-(NH)–O–PO32–+ H218O → NC·CO·NH2+18O·PO32–]. With an excess of cyanogen, the orthophosphate undergoes further cycles of 18O uptake from the water. In the presence of reducing sugars, the intermediate cyanogen–phosphate adduct acts as a phosphorylating agent, attacking the glycosidic hydroxy-groups to produce glycosyl phosphates. Cyanogen-promoted phosphorylation is suggested as a model for the prebiotic synthesis of sugar phosphates.