D-Glucose 1-phosphate formation by cyanogen-induced phosphorylation of D-glucose. Synthesis, mechanism, and application to other reducing sugars

Abstract

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 + HPO₄^2–→ NC–C(NH)–O·PO₃^2–] which then undergoes hydrolysis to produce ¹⁸O-labelled orthophosphate [NC–C-(NH)–O–PO₃^2–+ H₂¹⁸O → NC·CO·NH₂+¹⁸O·PO₃^2–]. 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.