Co-factor for phosphofructokinase is

Many of the glycolytic enzymes are sensitive to Mg2+. The most impoant effect is due to MgATP2-being a cofactor for a number of these enzymes while other chelation forms are inactive or inhibitory. The means by which Mg2+ and Mg2+ chelates of adenine nucleotides regulate the most impoant glycolytic enzymes--hexokinase, phosphofructokinase, aldolase, phosphoglycerate kinase, and pyruvate kinaseRef: DM Vasudevan, 7th edition