PFKFB (6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase) is a bifunctional enzyme that regulates the steady-state concentration of fructose-2,6-bisphosphate, which is a potent activator of the key regulatory enzyme of glycolysis, phosphofructokinase. PFKFB3 (iPFK2) is one of four tissue-specific PFKFB isozymes that have been identified to date. PFKFB3 also has been implicated in the high glycolytic rate of cancer cells that occurs despite adequate oxygen, a phenomenon known as the Warburg effect. We have isolated and characterized the human PFKFB3 genomic sequence, which spans a region of 32.5 kb and which has a single chromosomal locus. Determination of the exon-intron splice junctions established that PFKFB3 is encoded by 19 exons of which only 15 are normally expressed. Exon sizes range between 23 and 208 bp, the largest intron is 10,286 bp long. The full-length human PFKFB3 open reading frame is 4,675 bp long and encodes a 590 aa protein with a predicted molecular weight of 66.9 kDa and an isoelectric point of 8.64. Fluorescence in situ hybridization analysis localized the human PFKFB3 gene to chromosome 10p15.3-p15.2, and its locus is 3 million bp centromeric to PFKP, the platelet-type phosphofructokinase. PFKFB3 has been shown to be abundantly expressed in human tumors and its expression linked to long-standing observations concerning the apparent coupling of enhanced glycolysis and cell proliferation.

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