ACS Biochemistry Practice Exam – Prep Guide, Practice Test & Questions

The main function of RuBisCO activase is to facilitate the activation of the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). Specifically, it assists in the removal of ribulose-1,5-bisphosphate (RuBP) from the enzyme's active site to enable the process of carbamoylation. This is important because RuBP must be bound to RuBisCO in order for the enzyme to catalyze its reaction, but when the reaction is not proceeding (for example, when there is a high concentration of oxygen relative to carbon dioxide), RuBP can become a bottleneck, preventing effective carbon fixation. RuBisCO activase helps clear out this substrate so that RuBisCO can be effectively carbamoylated and remain functional.

The other options do not accurately describe the primary role of RuBisCO activase. For example, inhibiting RuBisCO's activity would actually hinder photosynthesis, which this enzyme helps to promote. Triggers of ATP production fall outside the specific role of RuBisCO activase, although ATP is certainly critical in the broader context of photosynthesis. Lastly, stimulating malate transport is not a direct function of RuBisCO