Which enzyme is commonly involved in the irreversible step of glycolysis?

Which enzyme is commonly involved in the irreversible step of glycolysis?

• A. Isocitrate Dehydrogenase
• B. Hexokinase
• C. Fumarase
• D. Succinyl-CoA

Answer: (B)

In glycolysis, one of the essential enzymes is hexokinase, which catalyzes the phosphorylation of glucose to glucose-6-phosphate. This reaction is a key regulatory point and is considered irreversible under physiological conditions due to its large negative ΔG, meaning it strongly favors the forward reaction. This step is crucial because it traps glucose inside the cell and commits it to further metabolism through glycolysis. Isocitrate dehydrogenase is involved in the citric acid cycle (Krebs cycle) and participates in the oxidative decarboxylation of isocitrate to alpha-ketoglutarate. Fumarase is also part of the citric acid cycle, catalyzing the hydration of fumarate to malate. Succinyl-CoA is a product of the citric acid cycle and is involved in the conversion of succinate to succinyl-CoA. While these enzymes are important for cellular metabolism, they are not directly involved in the glycolytic pathway. Hexokinase’s role in glycolysis is fundamental because it initiates the process of converting glucose into a usable form of energy, making it crucial for the regulation and flow of the entire pathway.

In glycolysis, one of the essential enzymes is hexokinase, which catalyzes the phosphorylation of glucose to glucose-6-phosphate. This reaction is a key regulatory point and is considered irreversible under physiological conditions due to its large negative ΔG, meaning it strongly favors the forward reaction. This step is crucial because it traps glucose inside the cell and commits it to further metabolism through glycolysis.

Isocitrate dehydrogenase is involved in the citric acid cycle (Krebs cycle) and participates in the oxidative decarboxylation of isocitrate to alpha-ketoglutarate. Fumarase is also part of the citric acid cycle, catalyzing the hydration of fumarate to malate. Succinyl-CoA is a product of the citric acid cycle and is involved in the conversion of succinate to succinyl-CoA. While these enzymes are important for cellular metabolism, they are not directly involved in the glycolytic pathway.

Hexokinase’s role in glycolysis is fundamental because it initiates the process of converting glucose into a usable form of energy, making it crucial for the regulation and flow of the entire pathway.