2phosphoglykolate

2-Phosphoglycolate, also known as 2-PG, is a two-carbon organic molecule that plays a crucial role in photorespiration in plants. It is formed when ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), the enzyme responsible for carbon fixation during photosynthesis, mistakenly binds oxygen instead of carbon dioxide to its substrate, RuBP. This oxygenation reaction leads to the production of one molecule of 3-phosphoglycerate and one molecule of 2-phosphoglycolate.

2-Phosphoglycolate is considered a metabolic dead end as it cannot be directly re-assimilated into the Calvin cycle. Instead, it must be processed through a complex salvage pathway, known as the photorespiratory pathway, which involves several organelles including chloroplasts, peroxisomes, and mitochondria. This pathway converts 2-phosphoglycolate back into 3-phosphoglycerate, a molecule that can re-enter the Calvin cycle.

The photorespiratory pathway, initiated by the production of 2-phosphoglycolate, is often viewed as a wasteful process because it consumes energy (ATP and reducing power) and releases previously fixed carbon dioxide, thereby reducing the net efficiency of photosynthesis, especially under conditions of high light intensity and low CO2 concentration. However, it is also believed to play important roles in protecting plants from photooxidative damage under stress conditions and in nitrogen assimilation. Research continues to explore the precise functions and metabolic significance of 2-phosphoglycolate and the photorespiratory pathway in plant physiology.