Learning RuBisCO's birth and subsequent environmental adaptation.

It is believed that organisms that first appeared after the formation of the earth lived in a very limited environment, making full use of the limited number of genes. From these early organisms' genes, more were created by replication, mutation, recombination, translocation, and transmission of other organisms' DNA; thus, it became possible for ancient organisms to grow in various environments. The photosynthetic CO-fixing enzyme RuBisCO (ribulose 1,5-bisphosphate carboxylase/oxygenase) began to function in primitive methanogenic archaea and has been evolved as a central CO-fixing enzyme in response to the large changes in CO and O concentrations that occurred in the subsequent 4 billion years. In this review, the processes of its adaptation to be specialized for CO fixation will be presented from the viewpoint of functions and structures of RuBisCO.