The Cori cycle involves several enzymes, primarily within the liver and muscles. Key enzymes are involved in both glycolysis (in muscle) and gluconeogenesis (in the liver).
Here's a breakdown of the enzymes central to the Cori cycle:
- Lactate Dehydrogenase (LDH): This is arguably the most important enzyme specifically associated with the Cori cycle. LDH catalyzes the reversible conversion of pyruvate to lactate in muscle (during anaerobic glycolysis) and the reverse reaction in the liver (converting lactate back to pyruvate for gluconeogenesis).
Enzymes involved in Gluconeogenesis (Liver): These enzymes help convert pyruvate (derived from lactate) back into glucose.
- Pyruvate Carboxylase: Converts pyruvate to oxaloacetate.
- Phosphoenolpyruvate Carboxykinase (PEPCK): Converts oxaloacetate to phosphoenolpyruvate.
- Fructose-1,6-bisphosphatase: Converts fructose-1,6-bisphosphate to fructose-6-phosphate.
- Glucose-6-phosphatase: Converts glucose-6-phosphate to glucose. (Present only in the liver and kidney).
Enzymes involved in Glycolysis (Muscle): These enzymes are part of the process that breaks down glucose to pyruvate, which is then converted to lactate.
- Hexokinase/Glucokinase: Phosphorylates glucose to glucose-6-phosphate.
- Phosphofructokinase-1 (PFK-1): Phosphorylates fructose-6-phosphate to fructose-1,6-bisphosphate.
- Pyruvate Kinase: Converts phosphoenolpyruvate to pyruvate.
In summary, while many enzymes play roles in the Cori cycle, lactate dehydrogenase (LDH) is the enzyme directly responsible for converting pyruvate to lactate in muscle and lactate back to pyruvate in the liver, thus forming the crucial link between glycolysis in muscle and gluconeogenesis in the liver that defines the cycle.
