Meta-Biol

• Pathways

The gamma-glutamyl cycle is a six-enzyme cycle that represents the primary pathway for glutathione synthesis and degradation. One step is the cleavage of 5-oxo-L-proline (OPRO) to form L-glutamate, coupled to the hydrolysis of ATP. This is catalysed by 5-oxoprolinase (OPLAH) is a homodimeric, cytosolic protein. Defects in OPLAH can cause 5-oxoprolinase deficiency (OPLAHD; MIM:260005), an extremely rare disorder of the gamma-glutamyl cycle about which debate continues as to whether it is a disorder or just a biochemical condition with no adverse clinical effects apart from 5-oxoprolinuria. Mutations that can cause OPLAHD are S323R, V1089I and H870Pfs*92 (Calpena et al. 2013, Almaghlouth et al. 2012).