Succinyl coenzyme A synthetase

Succinyl -CoA synthetase ( SCS) (also: succinate -CoA ligase ) enzymes are complexes of the citric acid cycle in all living things. The SCS catalyze a reaction equilibrium between succinate and coenzyme A on the one hand and succinyl - CoA consumption / income of the high-energy GTP ( EC 6.2.1.4 ) or ATP ( EC 6.2.1.5 ) on the other.

The simplified equation of this equilibrium is:

The energy of the cleavage of the succinyl -CoA is used for the formation of GTP / ATP. The citric acid cycle of the reaction left to right and a molecule of ATP / GTP runs is obtained. In the reductive citric acid cycle found in some bacteria, the reverse reaction takes ( then the SCS are called succinate Thiokinasen ).

The GDP- forming SCS come in all living things before ( in eukaryotes in the mitochondria ), while those found ADP- forming addition in eukaryotes in the cytosol. In bacteria, the SCS form heterotetramers. In humans, a GDP- and an ADP -forming isozyme - dimer (gene name SUCLG1 / 2 and SUCLG1/A2 ) is known. Mutations in the human SUCLG1 gene can cause ( rare ) enzyme deficiency in the embryo and this infantile lactic acidosis, which runs fatal. Defects in SUCLA2 can lead to a very rare mitochondrial metabolic disorder with organ damage. In both cases, methylmalonic acid is detectable in the urine.