Why is the RuBisCo enzyme more appropriately called RUBP carboxylase-oxygenase and what important role does it play in photosynthesis ?

Explanation

RuBP carboxylase and oxygenase has dual nature. It has affinity for both `CO_(2)` and `O_(2)` . Thus, the concentration of two determines which of the two willl bind to the enzymes.
Consider the following two situations.
(i) In a normal condition when `CO_(2)` and `O_(2)` concentration are normal, if acts as carboxylase and fix `CO_(2)` by combining with ribulose bisphosphate and `C_(3)` cycle operates normally, producing glucose molecules as an first product of photosynthesis.
(ii) If `O_(2)` concentration goes up and `CO_(2)` goes down, it starts acting as an oxygenase enzyme and `C_(2)` cycle ( photorespiration ) starts where RuBP binds with `O_(2)` to form phosphoglycolate.
`C_(4)` plants have mechanisms to increase the concentration of `CO_(2)` at enzyme site, and increasing the intercellular concentration of `CO_(2)`. Thus, here RuB is Co acts as carboxylase, minimising the effect of oxygenase.