Crystal Structure of Thermus thermophilus Δ1-Pyrroline-5-carboxylate Dehydrogenase

Abstract Δ 1 -pyrroline-5-carboxylate dehydrogenase (P5CDh) plays an important role in the metabolic pathway from proline to glutamate. It irreversibly catalyzes the oxidation of glutamate-γ-semialdehyde, the product of the non-enzymatic hydrolysis of Δ 1 -pyrroline-5-carboxylate, into glutamate with the reduction of NAD + into NADH. We have confirmed the P5CDh activity of the Thermus thermophilus protein TT0033 ( Tt P5CDh), and determined the crystal structure of the enzyme in the ligand-free form at 1.4 A resolution. To investigate the structural basis of Tt P5CDh function, the Tt P5CDh structures with NAD + , with NADH, and with its product glutamate were determined at 1.8 A, 1.9 A, and 1.4 A resolution, respectively. The solved structures suggest an overall view of the P5CDh catalytic mechanism and provide insights into the P5CDh deficiencies in the case of the human type II hyperprolinemia.