Tau protein possesses pyruvate kinase (PK) activity, which is capable of phosphorylating ADP into ATP. ATP has the ability to inhibit PK kinase activity. When the Tau protein's D13 binds to ATP, it inhibits pyruvate kinase activity, and when it binds to ADP, it activates.Phospases can convert ATP to ADP by self-dephosphorylating tau protein. Tau protein catalyzes the dephosphorylation process, converting ATP at the D13 binding site to ADP and activating pyruvate kinase activity. Tau protein's pyruvate kinase activity (PK) speeds up the last step of glycolysis by changing phosphoenolpyruvate (PEP) into pyruvate and phosphorylating ADP at the D13 binding site to ATP at the same time. This subsequently inhibits the pyruvate kinase activity.