Gluconeogenesis Reactions The reaction sequence in gluconeogenesis is largely the reverse of glycolysis. Recall, however, that three glycolytic reactions (the reactions catalyzed by hexokinase, PFK-1, and pyruvate kinase) are irreversible. In gluconeogenesis, alternate reactions catalyzed by different enzymes are used to bypass these obstacles. The reactions unique to gluconeogenesis are listed next. The entire gluconeogenic pathway and its relationship to glycolysis are illustrated in Figure 8.10. The bypass reactions of gluconeogenesis are as follows: