## Regulation of Glycolysis: Phosphofructokinase-1 (PFK-1) **Key Regulatory Enzyme:** PFK-1 catalyzes the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate, the committed and rate-limiting step of glycolysis. **Thermodynamic Properties:** - ΔG°' = −14.2 kJ/mol (highly negative, essentially irreversible under physiological conditions) - This irreversibility makes it an ideal control point **Allosteric Regulation:** - **Inhibitors:** ATP (high energy signal), Citrate (abundant biosynthetic precursors) - **Activators:** AMP, ADP (low energy signals), Fructose-2,6-bisphosphate (F-2,6-BP, most potent activator) **Mnemonic:** "PFK is the **Committed** step—it's where glycolysis commits to proceeding. It's regulated by energy status (ATP/AMP) and biosynthetic needs (Citrate)." **Clinical Pearl:** This is the primary control point for glycolytic flux. When energy is abundant (high ATP, high citrate), glycolysis is inhibited to prevent wasteful ATP production.
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