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Enzyme-to-enzyme tunnelling between phosphoglucoisomerase and phosphofructokinase

par Zahner, Dagmar ;Malaisse, Willy
Référence International Journal of Biochemistry, 25, 9, page (1303-1307)
Publication Publié, 1993

Article révisé par les pairs

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Résumé :

Cross-linked and permeabilized rat erythrocytes were incubated for 2-5 min at 37°C in the presence of ATP and either D-[U-14C]glucose 6-phosphate (3 mM) mixed with unlabelled D-fructose 6-phosphate (1 mM) or D-[U-14C]fructose 6-phosphate (1 mM) mixed with unlabelled D-glucose 6-phosphate (3 mM). The contribution of molecules derived from the radioactive ketohexose ester relative to the total amount of newly formed D-fructose 1,6-bisphosphate was lower than the time-related averaged value for such a relative contribution in the pool of D-fructose 6-phosphate. From such a difference, it was calculated that, under the present experimental conditions, 13.1 ± 2.0% of the molecules of D-fructose 1,6-bisphosphate formed during incubation are directly derived from D-glucose 6-phosphate by a process of enzyme-to-enzyme channelling between phosphoglucoisomerase and phosphofructokinase, rather than originating from the free pool of D-fructose 6-phosphate. A comparable value of 13.2 ± 3.2% was reached when the process of enzyme-to-enzyme tunnelling was judged from the 3H/14C ratio in D-fructose 1,6-bisphosphate formed by permeabilized erythrocytes exposed for 5-15 min to D-glucose 6-phosphate (3 or 5 mM) mixed with tracer amounts of both D-[l-14C]glucose 6-phosphate and D-[2-3H]glucose 6-phosphate.