||"Calculations of the amount of RuBPCase on the earth are necessarily approximate. The total amount of carbon fixed per year by land plants is estimated to be 50×10^15 g [ref 10, Woodwell, G. M. (1978) Sci. Am. 238, 34-43]. From turnover number of the enzyme it can be shown that the amount of RuBPCase required to fix this quantity of carbon is about 4×10^13 g of protein, or 10^4 g for each person [as of 1979, as of 2015 ~5×10^3g/per person]. The total biomass on the earth has been estimated at 2×10^19 g [ref 11, ‘Energy Resources’ (1973) Open University Second Level Course in Science, p. 120, The Open University Press, Milton Keynes, U.K.]. If it is assumed that 0.1% of this biomass is protein, then the ratio of RuBPCase to total protein is 4×10^13/2×10^16 or 0.2%. The next most abundant protein is probably actin, but no reasonable estimate of its total quantity is possible."