<prompt> Which element is required by phosphofructokinase?MagnesiumInorganic phosphateManganeseCopper  <response>: Phosphofructokinase PFK is --300 amino acids in length, and structural studies of the bacterial enzyme have shown it comprises two similar alphabeta lobes: one involved in ATP binding and the other housing both the substrate-binding site and the allosteric site a regulatory binding site distinct from the active site, but that affects enzyme activity. The identical tetramer subunits adopt 2 different conformations: in a closed state, the bound magnesium ion bridges the phosphoryl groups of the enzyme products ADP and fructose-1,6- bisphosphate; and in an open state, the magnesium ion binds only the ADP, as the 2 products are now fuher apa 