Which enzyme catalyzes the carboxylation of RuBP in the dark reactions?

The enzyme that catalyzes the carboxylation of ribulose 1,5-bisphosphate (RuBP) in the dark reactions, which are also known as the Calvin cycle, is RuBisCo (ribulose bisphosphate carboxylase/oxygenase). This enzyme plays a critical role in photosynthesis by facilitating the first major step of carbon fixation. During this process, RuBisCo helps incorporate carbon dioxide into RuBP, resulting in a six-carbon compound that eventually splits into two molecules of 3-phosphoglycerate (3-PGA).

RuBisCo is unique because it can catalyze both carboxylation and oxygenation reactions, which are essential for the process of photosynthesis. However, its primary function in this context is to catalyze the reaction that incorporates carbon dioxide into the Calvin cycle, making it a key player in the conversion of inorganic carbon into an organic form.

In contrast, the other enzymes mentioned have different functions: Phosphofructokinase is involved in glycolysis, PEP carboxylase is used in C4 photosynthesis and assists in fixing carbon in certain plant types, while NADP+ reductase is involved in the light reactions of photosynthesis