Articles | Volume 3, issue 1
Research article
12 Mar 2012
Research article |  | 12 Mar 2012

The regulation of the air: a hypothesis

E. G. Nisbet, C. M. R. Fowler, and R. E. R. Nisbet

Abstract. We propose the hypothesis that natural selection, acting on the specificity or preference for CO2 over O2 of the enzyme rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), has controlled the CO2:O2 ratio of the atmosphere since the evolution of photosynthesis and has also sustained the Earth's greenhouse-set surface temperature. Rubisco works in partnership with the nitrogen-fixing enzyme nitrogenase to control atmospheric pressure. Together, these two enzymes control global surface temperature and indirectly the pH and oxygenation of the ocean. Thus, the co-evolution of these two enzymes may have produced clement conditions on the Earth's surface, allowing life to be sustained.