 The members of the PfkB/RK family are identified by the presence of three conserved sequence motifs.The structures of several PfK family of proteins have been determined from a number of organisms and the enzymatic activity of this family of protein shows a dependence on the presence of pentavalent ions.PFK is found in isoform versions in skeletal muscle (PFKM), in the liver (PFKL), and from platelets (PFKP), allowing for tissue-specific expression and function.