For carboxylation reaction in $$C4$$ plants which amongst the following enzymes $$is/are$$ involved:(a) $$RuBisCO(b)$$ $$PEPcase(c)$$ Pyruvate orthophosphate $$dikinase(d)$$ $$Ribulose-5-phosphate$$ kinase.

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Infinity Learn · Accepted Answer

The primary $$CO2$$ acceptor in $$C4$$ cycle is a $$3-carbon$$ molecule phosphoenol pyruvate (PEP) and is present in the mesophyll cells. The enzyme responsible for this fixation is PEP carboxylase or PEPcase. It then forms other $$4-carbon$$ compounds like malic acid or aspartic acid in the mesophyll cells itself, which are transported to bundle sheath cells. In bundle sheath cells these $$C4$$ acids are broken down to release $$CO2$$ and $$3-carbon$$ molecule (pyruvic$$ $$acid). The $$CO2$$ released in the bundle sheath cells enters the $$C3$$ or the Calvin cycle. In the Calvin cycle again carboxylation occurs with the help of the enzyme RuBiSCO.

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