The most abundant protein catalyses the following reaction
Carboxylation
The most abundant protein in the biosphere is RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase). It catalyzes the primary chemical reaction by which inorganic carbon permanently enters the biosphere. It catalyzes the carboxylation of ribulose-1,5-bisphosphate (RuBP).