Question

rubisco is an enzyme acts both as carboxylasa and oxygenase. Explain

Answer 1

RuBP Carboxylase-Oxygenase (Ribulose- 1, 5-bisphosphate Carboxylase-Oxygenase) is also called RUBISCO. It is the most abundant enzyme complex found on the earth. It can act on the two substrates: Carbon dioxide (carboxylase activity- for carbon dioxide assimilation into glucose during photosynthesis) and Oxygen ( oxygenase activity-causing photorespiration , decreasing the photosynthetic efficiency of plants) . There is competition between CO₂ and O₂ to bind with active site of RuBisCO for combining with RUBP. The competition between their Carboxylase-Oxygenase activity is dependent upon the relative concentration of carbon dioxide and oxygen and affinity of RUBISCO for these gases. Fortunately, RUBISCO has more affinity (80 times more) for carbon dioxide than oxygen. Under higher concentration condition of carbon dioxide than oxygen, obviously RUBISCO shows its carboxylase activity . While, under very high concentration condition of oxygen than carbon dioxide , RUBISCO may shows its oxygenase activity.