Ribulose-1,5-bisphosphate carboxylase/oxygenase commonly known by the abbreviation RuBisCO, is an enzyme involved in the first major step of carbon fixation, a process by which atmospheric carbon dioxide is converted by plants to energy-rich molecules such as glucose. In chemical terms, it catalyzes the carboxylation of ribulose-1,5-bisphosphate (also known as RuBP) . It is probably the most abundant enzyme on Earth. The enzyme usually consists of two types of protein subunit, called the large chain (RbcL) and the small chain (RbcS) .
