Question
The enzyme required for carboxylation in the Calvin cycle is :
This question was previously asked in
NEET UG Re-Exam 2026 Question Paper (21-Jun-2026)
The correct answer is
RuBP carboxylase-oxygenase
Understanding the Calvin cycle is key to identifying the enzyme responsible for carboxylation.
Calvin Cycle Carboxylation Enzyme
The Calvin cycle is the primary pathway for carbon fixation in photosynthesis. The first step, carboxylation, involves attaching carbon dioxide (CO2) to Ribulose-1,5-bisphosphate (RuBP).
Identifying the Correct Enzyme
The specific enzyme catalyzing this crucial carboxylation reaction is RuBP carboxylase-oxygenase, commonly known as Rubisco.
- RuBP carboxylase-oxygenase directly facilitates the addition of CO2 to RuBP, initiating the cycle.
Evaluating Other Options
The other options are incorrect because:
- Carboxypeptidase: This enzyme breaks down peptides, acting on proteins, not involved in carbon fixation.
- PEP carboxylase: While involved in carbon fixation, it's primarily active in C4 and CAM plants, fixing CO2 into phosphoenolpyruvate (PEP), not directly in the Calvin cycle's initial carboxylation step as described here.
- Hexokinase: This enzyme phosphorylates glucose, the first step of glycolysis, unrelated to the Calvin cycle.
Therefore, the enzyme required for carboxylation in the Calvin cycle is RuBP carboxylase-oxygenase.
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