Ribulose-1,5-diphosphate carboxylase and oxygenase from green plants are two different enzymes.

Ribulose-1,5-diphosphate oxygenase is shown to be an enzyme different from ribulose-1,5-diphosphate carboxylase. The enzymes can be separated from each other by a preparation method employing gel filtration at a pH of 8.3 which is higher than that previously used. The oxygenase activity is correlated with a blue color and a characteristic Cu EPR signal. This indicates that the oxygenase is a copper-containing enzyme.