An allosteric enzyme that regulates glycolysis by catalyzing the transfer of a phosphate group from ATP to fructose-6-phosphate to yield fructose-1,6-bisphosphate. In the humans, 6-phosphofructose-1-kinase isozyme C is found in platelets, brain, heart, kidney, colon and testis. This isozyme C can exist as the homotetramer of C subunits (P subunits), or heterotetramer of C type and L type subunits.