Rubisco can also act as an oxygenase breaking down ribulose bisphosphate in the presence of oxygen to glycerate 3-phosphate and phosphoglycolic aid.This reaction forms the basis of PHOTOREESPIRATION.

• 此酶在有氧的情况下可为氧化酶，分解核酮糖-1，5-二磷酸生产3-磷酸甘油和磷酸乙醇酸，这一反应是光呼吸的基础。