Structural subunit of pyrophosphate--fructose 6-phosphate 1-phosphotransferase. Not required for catalytic activity. Fine-tunes allosteric regulation of the ATP-PFK by ATP, fructose 2,6-bisphosphate and AMP. Carbohydrate degradation; glycolysis; D-glyceraldehyde 3-phosphate and glycerone phosphate from D-glucose: step 3/4. Heterododecamer of 4 alpha, 4 beta and 4 gamma chains. The gamma chain bridges the N-terminal halves of the alpha and beta subunits. This subunit is only found in some Pichia species.