ENZYMATIC RATES. “RuBisCo “fixes” CO2 by attaching it to a sugar called ribulose bisphosphate. But it is easily confused, and sometimes picks up an oxygen molecule and attaches that instead, causing a series of reactions that result in the loss of both carbon and energy. Worse still, RuBisCo enzymes catalyse the reaction of only about three molecules per second. Other common enzymes catalyse tens of thousands.”
http://answersinscience.org/EvolGreatestMistakes-NewSci%20081107.pdf