Glycine cleavage system



The glycine cleavage system is also known as the glycine decarboxylase complex or GCS. The system is a series of enzymes that are triggered in response to high concentrations of the amino acid glycine. The glycine cleavage system is composed of four proteins: the T-protein, P-protein, L-protein, and H-protein. They do not form a stable complex, so it is more appropriate to call it a "system" instead of a "complex"

Function
In plants the glycine cleavage system is coupled to serine hydroxymethyltransferase to give an overall reaction of:
 * 2 glycine + NAD+ + H2O → serine + CO2 + NH3 + NADH + H+

This reaction, and by extension the glycine cleavage system, is required for photorespiration in C3 plants. Together the proteins involved in these reactions comprise about half the proteins in mitochondria from spinach and pea leaves.