Gamma-glutamyl phosphate reductase (GPR), aldehyde dehydrogenase families 18 and 19
Gamma-glutamyl phosphate reductase (GPR), a L-proline biosynthetic pathway (PBP) enzyme that catalyzes the NADPH dependent reduction of L-gamma-glutamyl 5-phosphate into L-glutamate 5-semialdehyde and phosphate. The glutamate route of the PBP involves two enzymatic steps catalyzed by gamma-glutamyl kinase (GK, EC 18.104.22.168) and GPR (EC 22.214.171.124). These enzymes are fused into the bifunctional enzyme, ProA or delta(1)-pyrroline-5-carboxylate synthetase (P5CS) in plants and animals, whereas they are separate enzymes in bacteria and yeast. In humans, the P5CS (ALDH18A1), an inner mitochondrial membrane enzyme, is essential to the de novo synthesis of the amino acids proline and arginine. Tomato (Lycopersicon esculentum) has both the prokaryotic-like polycistronic operons encoding GK and GPR (PRO1, ALDH19) and the full-length, bifunctional P5CS (PRO2, ALDH18B1).