Question : RUBISCO is an enzyme that acts both as a carboxylase and oxygenase. Why do you think RUBISCO carries out more carboxylation in C_(4) aplants?

Question : RUBISCO is an enzyme that acts both as a carboxylase and ox

1.	Question : RUBISCO is an enzyme that acts both as a carboxylase and oxygenase. Why do you think RUBISCO carries out more carboxylation in C_(4) aplants?
Answer» Solution :RUBISCO is the most abundant enzyme in the world and can bind to both `CO_(2) and O_(2)`on its active sites. RUBISCO has much GREATER affinity for `CO_(2)`than` O_(2),` This binding is competitive. It depends on the relative concentration of `O_(2) andCO_(2)`and that determines which of the TWO will bind the enzyme. In `C_(4)`PLANTS the photorespiration does not take place. Also the plants have a mechanism due to which `CO_(2)`concentration at enzyme site increases. This is due to SPLITTING of `C_(4)`acid in mesophyll leading to RELEASE of `CO_(2),` thereby increasing the concentration of `CO_(2).` This increases the carboxylase activity of RUBISCO, and decreases the oxygenase activity.