Which of the following enzymes is NOT an irreversible enzyme in glycolysis?

In the context of glycolysis, understanding which enzymes are classified as irreversible is important for recognizing key regulatory points in the metabolic pathway. The correct answer identifies pyridoxal kinase as the enzyme that is not classified as irreversible in glycolysis.

Pyridoxal kinase functions in the phosphorylation of pyridoxal to form pyridoxal phosphate, a coenzyme involved in various biochemical reactions, particularly those related to amino acids. However, this enzyme is not part of the glycolytic pathway, which involves the conversion of glucose into pyruvate through several specific reactions.

In contrast, glucokinase, PFK-1 (phosphofructokinase-1), and pyruvate kinase are considered key regulatory enzymes in glycolysis that facilitate irreversible reactions. Glucokinase catalyzes the phosphorylation of glucose to glucose-6-phosphate. PFK-1 is often termed the "committed step" of glycolysis, converting fructose-6-phosphate to fructose-1,6-bisphosphate. Pyruvate kinase catalyzes the conversion of phosphoenolpyruvate to pyruvate, releasing energy in the form of ATP. Each of these enzymes plays a critical role in controlling the