Glycolysis and Gluconeogenesis:
1 Glucose à glucose-6-phosphate [glucokinase/hexokinase] , <à fructose-6-phosphate requires ATP. Reverse reaction done by glucose-6-phosphatase (deficiency of which leads to Von Gierke’s). An impaired ability to make glucose in the liver from either gluconeogenesis or break down glucose from glycogen.
Hexose monophosphate shunt:
- A way to generate NADPH (first 3 steps which are oxidative and make 2 NADPH) which is used for anabolic process (lipid and nucleic acid synthesis) and to reduce oxidative stress (with glutathione).
- Also makes 5 carbon sugars (pentoses) – which are used in making nucleotides and nucleic acids.
- Takes place in cytosol.
- An alternative to glycoslysis (which makes NADH).
HMP Shunt:
Glucose-6-phosphate à 6-phosphogluconolactone, NADPH à6-phosphogluconateà x, NADPHà Ribulose-5-phosphate àààFructose-6-phosphate à fructose-1,6-bisphosphate
- The first step done by G-6PD (if deficient, get hemolytic anemia because RBCs depend on glycolysis alone to metabolize glucose).
Glycolysis Continued……
Fructose-6-phosphate à Fructose-1,6-bisphosphate
(is the rate-limiting step in glycolysis)
- Catalyzed by PFK-1 (phosphfructokinase-1)
another possibility for F-6-P:
Fructose-6-phosphate à fructose-2,6-BP
- Catalyzed by PFK-2 (which is active when dephosphorylated, in liver)
- F-2,6-BP is the most potent activator of PFK-1
Glycolysis continued…
Fructose-1,6-bisphosphateà -> Glyceraldehyde-3-P, DHAP -> 1,3-bis-phosphoglycerate -> 3-phosphoglycerate -> 2-phosphoglycerate -> Phosphoenolpyruvate -> Pyruvate -> Acetyl-CoA ->