Regulatory subunit of pyrophosphate--fructose 6-phosphate 1-phosphotransferase. Allosterically activated by fructose 2,6-bisphosphate. Carbohydrate degradation; glycolysis; D-glyceraldehyde 3-phosphate and glycerone phosphate from D-glucose: step 3/4. Tetramer of two alpha (regulatory) and two beta (catalytic) chains. Expressed in leaves, roots, and flowers (e.g. sepals, petals, stamen and gynoecium). By sucrose, glucose, and fructose. Retarded growth and reduced pyrophosphate--fructose 6-phosphate 1-phosphotransferase (PFP) activity. Belongs to the phosphofructokinase type A (PFKA) family. PPi-dependent PFK group II subfamily. Clade 'Long' sub-subfamily.