6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 4 also known as PFKFB4 is an enzyme which in humans is encoded by the PFKFB4 gene. The bifunctional 6-phosphofructo-2-kinase (EC 2.7.1.105)/fructose-2,6-bisphosphatase (EC 3.1.3.46) (PFKFB) regulates the steady-state concentration of fructose 2,6-bisphosphate, an activator of a key regulatory enzyme of glycolysis, phosphofructokinase.