With an activity of only 3 molecules per second, its inefficiency is compounded by its inability to distinguish between oxygen and carbon dioxide.  
Photosynthetic bacteria build a version of this enzyme that contains only two chains, yet functions as well as the plant version that contains 8 large chains and 8 small chains.  Three amino acids, including a modified form of lysine, surround its active site, which is arranged around a magnesium ion.  With an activity of only 3 molecules per second, its inefficiency is compounded by its inability to distinguish between oxygen and carbon dioxide.  Its function is to create organic carbon from carbon dioxide.  FTP, name this key enzyme in the Calvin Cycle that is also the most abundant protein on earth.
Photosynthetic bacteria build a version of this enzyme that contains only two chains, yet functions as well as the plant version that contains 8 large chains and 8 small chains.  
{rubisco} or {ribulose bisphosphate carboxylase/oxygenase}