Regulation of Glycolysis

• Regulation of glycolysis for an exam in biochemistry or molecular biology
• Special enzymes focused on in this video:

  • Hexokinase
  • Phosphofructokinase 1
  • Pyruvate kinase
• Hexokinase:

  • Converts glucose into glucose 6-phosphate
  • Stimulated by glucose
  • Inhibited by glucose 6-phosphate
  • Allosteric regulation: glucose stimulates, glucose 6-phosphate inhibits
  • Hormonal regulation: insulin stimulates synthesis of more hexokinase
• Phosphofructokinase 1:

  • Phosphorylates fructose 6-phosphate into fructose 1,6-bisphosphate
  • Highly regulated step in glycolysis
  • Inhibited by ATP and citrate
  • Stimulated by high levels of ADP
• Pyruvate kinase:

  • Converts phosphoenolpyruvate (PEP) into pyruvate
  • Stimulated by fructose 1,6-bisphosphate
  • Inhibited by ATP and alanine
• High amounts of ADP stimulate the enzyme to signal low ATP levels and stimulate ATP production
• Fructose 6-phosphate can be converted into fructose 2,6-bisphosphate by a heteronuclear enzyme complex consisting of phosphofructokinase 2 and fructose 2,6-bisphosphatase
• Fructose 2,6-bisphosphate is a powerful regulator of phosphofructokinase 1, stimulating the enzyme to convert more fructose 6-phosphate into fructose 1,6-bisphosphate to make ATP
• Insulin stimulates the enzyme pyruvate kinase by removing phosphates, while glucagon inhibits it by phosphorylating the enzyme
• Inhibition of pyruvate kinase can occur with high ATP levels, long-chain fatty acyl CoAs, and too much acetyl CoA, indicating excessive energy production
• Fructose 1,6-bisphosphate acts as a feed-forward stimulator, preparing pyruvate kinase for increased activity in glycolysis
• Glyceraldehyde-3-phosphate dehydrogenase and pyruvate kinase are susceptible to inhibition by arsenate, which can bind in the place of phosphate and disrupt the enzyme's function