Another Form of Modified, Highly-Active 6-Phosphofructo-1-Kinase in Cancer Cells

Enhanced glycolytic flux is a hallmarks of cancer cells. Posttranslational modification of the key regulatory enzyme of glycolysis, 6-Phosphofructo-1- Kinase (Pfk1) might trigger metabolic flux deregulation. In the cancer cells the human 85 kDa muscle type nPfk-M enzyme can be proteolytically cleaved to form highly-active 47 kDa shorter fragments that retain activity but become resistant to feed-back inhibition. In several tumorigenic cell lines, no native 85 kDa liver type nPfk-L isoforms could be either found and only 70 kDa shorter fragments were detected by immune-blotting. To learn more about the cancer-specific modified sfPfk-L enzyme, the truncated human sfPfk-L gene encoding 70 kDa fragments was inserted into the pfk null yeast S.cerevisiae cell. The recombinant modified enzyme showed higher affinity toward the substrate fructose-6-phosphate, reduced sensitivity toward the citrate and ATP inhibition in respect to the recombinant native PFK-L enzyme. Partially purified cancer-specific sfPfk-L fragments lacking the C-portion of the enzyme showed some instability under the diluted conditions in the buffer in respect to the tetrameric native nPfk-L enzyme. Growth characterist