Rubisco primer

摘要

Ribulose 1,5-bisphosphate carboxylase-oxygenase (EC 4.1.1.39), named Rubisco, provides the main route for accumulation of organic carbon in the biosphere. As part of the Calvin cycle (also known as the photosynthetic carbon reduction cycle), Rubisco catalyses a sequence of reactions during photosynthesis that results in carbon assimilation through fixation of atmospheric carbon dioxide (CO_2), a process that underpins all life. Despite this critical role, Rubisco has the paradoxical distinction of being one of the most inefficient enzymes, fixing only a few CO_2 molecules per second. This is partly a consequence of the rapid fall in atmospheric CO_2 partial pressure (pCO_2) over geological timescales since Rubisco first appeared. Furthermore, Rubisco fails to differentiate efficiently between CO_2 and O_2, whose atmospheric concentration has risen rapidly (from near zero) over the same evolutionary timescale.