The bifunctional 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase(PFKFB) regulates the steady-state concentration of fructose-2,6-bisphosphate, a potent activator of a key regulatory enzyme of glycolysis, phosphofructokinase.The predicted PFKFB3 protein, which is 61% similar to human liver PFKFB, contains 529 amino acids and 7 potential phosphorylation sites. Northern blot analysis of first-trimester and term placentas detected a 4.5-kb PFKFB3 transcript.

PFKFB3 is expressed as a 58-kD protein. Molecular sieve analysis confirmed that PFKFB3 is bifunctional, although the phosphatase activity was low due to a mutation in an active site. The kinase activity was upregulated after phosphorylation by protein kinases.