In glycolysis the first commited step is catalysed by:

Fructose 6 Phosphate is phosphorylated to Fructose 1, 6 Bisphosphate by Phosphofructokinase I (PFK-I) Second irreversible step Major regulatory step of Glycolysis Committed step of GIycolysis because once Fructose 1, 6 Bisphosphate is formed it should undergo glycolysis Otherwise called bottle neck of Glycolysis 1 ATP is utilized. Key Concept: First Committed step is catalyzed by Phosphofructokinase This is otherwise called the bottle neck of Glycolysis.