PFKFB3 is a gene that encodes the 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 enzyme in humans. It is one of 4 tissue-specific PFKFB isoenzymes identified currently (PFKFB1-4). PFKFB3 converts fructose-6-phosphate to fructose-2,6-bisP (F2,6BP). F2,6BP is a ‘potent’ allosteric activator of 6-phosphofructokinase-1 (PFK-1), stimulating glycolysis. In neurons, glucose is mainly metabolized through the pentose–phosphate pathway (PPP), which is required for NADPH(H+) regeneration and maintenance of neuronal redox status. This neuronal metabolic switch is dictated by the PFKFB3 activity. In neurons, PFKFB3 protein abundance is negligible due to the continuous proteasomal degradation of the enzyme. However, overexcitation of N-methyl-D-aspartate subtype of glutamate receptors (NMDAR), known as excitotoxicity, stabilizes PFKFB3 protein in neurons, resulting in a redirection of glucose flux from PPP to glycolysis, followed by low NADPH(H+) availability for proper GSH regeneration; this ultimately leads to oxidative stress and neuronal death. PFKFB3 is also associated with the Warburg effect because its activity increases the rate of glycolysis. PFKFB3 has been found to be upregulated in numerous cancers, including colon, breast, ovarian, and thyroid.
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