Photorespiration (also known as the
oxidative photosynthetic carbon cycle, or
C2 photosynthesis) refers to a process in
plant metabolism where the
enzyme RuBisCO oxygenates
RuBP, causing some of the energy produced by photosynthesis to be wasted. The desired reaction is the addition of
carbon dioxide to RuBP (
carboxylation), a key step in the
Calvin–Benson cycle, however approximately 25% of reactions by RuBisCO instead add oxygen to RuBP (
oxygenation), creating a product that cannot be used within the Calvin–Benson cycle. This process reduces the efficiency of photosynthesis, potentially reducing photosynthetic output by 25% in
plants. Photorespiration involves a complex network of enzyme reactions that exchange metabolites between
chloroplasts, leaf
peroxisomes and
mitochondria.
