PFK1, also known as PFKM, is a regulatory glycolytic enzyme. PFK1 converts fructose 6-phosphate and ATP into fructose 1,6-bisphosphate (through PFK-1), fructose 2,6-bisphosphate (through PFK-2) and ADP. It is a muscle-type isozyme. There are three phosphofructokinase isozymes in humans: muscle, liver and platelet. These isozymes function as subunits of the mammalian tetramer phosphofructokinase, which catalyzes the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate. Mutations in PFK1 gene have been related to glycogen storage disease type VII, also identified as Tarui disease.