The explanation for the blockade of glycolysis in early mouse embryos.
The reason for the failure of early-stage mouse embryos to grow on glucose alone was investigated by measurement of glucose-6-phosphate, fructose-1,6-bisphosphate plus triose phosphates, citrate, and malate in individual embryos during starvation and refeeding with glucose or glucose plus pyruvate. The results indicate a block at the 6-phosphofructokinase (EC 2.7.1.11) step at early stages, which is later removed. Although there seems to be no early difficulty in phosphorylation of glucose, maximum glucose-6-phosphate levels (and probably fructose-6-phosphate levels) are much lower at early stages than at later stages. The increase in fructose-6-phosphate with age may be the major cause of the increase in 6-phosphofructokinase activity. Unusually high citrate levels at all ages may help to keep this enzyme strongly inhibited until the increase in fructose-6-phosphate occurs. The changes in metabolite levels also indicate an early defect in mobilization of glycogen and a probably less important defect in the citrate cycle.
D000818:Animals; D002951:Citrates / Q000378:metabolism; D003470:Culture Media; D046508:Culture Techniques; D004622:Embryo, Mammalian / Q000201:enzymology / Q000378:metabolism*; D005636:Fructosephosphates / Q000378:metabolism; D005958:Glucosephosphates / Q000378:metabolism; D006019:Glycolysis; D006593:Hexokinase / Q000378:metabolism; D008293:Malates / Q000378:metabolism; D051379:Mice; D010732:Phosphofructokinase-1 / Q000378:metabolism; D006005:Phosphorylases / Q000378:metabolism
D002951:Citrates; D003470:Culture Media; D005636:Fructosephosphates; D005958:Glucosephosphates; D008293:Malates; D006005:Phosphorylases; D006593:Hexokinase; D010732:Phosphofructokinase-1