Fructose 2,6-bisphosphate and glucose 1,6-bisphosphate in avian and mammalian erythroid cells

Chicken erythrocytes contain fructose 2,6-P2 at a concentration (0.6 nmol/10(9) cells) lower than that of glucose 1,6-P2 (5.4 nmol/10(9) cells) and similar to that of 2,3-bis phosphoglycerate (1.2 nmol/10(9) cells). In chick embryo erythrocytes the content of both bisphosphorylated hexoses is much lower. They begin to increase at hatching and reach chicken values in a few days. Fructose 2,6-P2 at microM concentration activates phosphofructokinase from chicken erythrocytes and releases the inhibition produced by ATP, 2,3-bisphosphoglycerate and inositol hexaphosphate. Glucose 1,6-P2 has similar effects but at much greater concentration. Rabbit reticulocytes contain fructose 2,6-P2 at a concentration (39 pmol/10(9) cells) much lower than that of glucose 1,6-P2 (74 nmol/10(9) cells).