2. Covalent Modification of Enzyme- Hexokinase, phosphofructokinase and pyruvate kinase are key enzymes responsible for controlling glycolysis. Most of the typical protein kinases are regulated by a reversible phosphorylation and dephosphorylation. In the presence of low glucose in blood, pyruvate kinase is getting phosphorylated by cytosolic enzymes and phosphoryated pyruvate kinase is less active. Similarly in the presence of high blood glucose level, it remains as unphosphorylated and that relive the inhibition caused by phosphorylation (Figure 5.3, A).

Figure 5.3: Regulation of glycolysis: (A) Covalent Modification (B) Alloteric regulation of enzymes of glycolysis.