PFKM

6-phosphofructokinase, muscle type is an enzyme that in humans is encoded by the PFKM gene on chromosome 12. Three phosphofructokinase isozymes exist 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. Tetramer composition varies depending on tissue type. This gene encodes the muscle-type isozyme. Mutations in this gene have been associated with glycogen storage disease type VII, also known as Tarui disease. Alternatively spliced transcript variants have been described.[provided by RefSeq, Nov 2009]

Structure

Gene

This gene is found on chromosome 12. The coding region in PFKM only shares a 68% similarity with that of the liver-type PFKL.

Protein

This 85-kDa protein is one of two subunit types that comprise the seven tetrameric PFK isozymes. The muscle isozyme (PFK-1) is composed solely of PFKM. The liver PFK (PFK-5) contains solely the second subunit type, PFKL, while the erythrocyte PFK includes five isozymes composed of different combinations of PFKM and PFKL. These subunits evolved from a common prokaryotic ancestor via gene duplication and mutation events. Generally, the N-terminal of the subunits carries out their catalytic activity while the C-terminal contains allosteric ligand binding sites. In particular, the binding site for the PFK inhibitor citrate is found in the PFKL C-terminal region.