Oxidation of amino acids, like proline catabolism, is a central part of energy metabolism. Proline is oxidized to glutamate by two enzymes: proline dehydrogenase (PRODH) and 1-pyrroline-5-carboxylate dehydrogenase (P5CDH). PRODH catalyzes the first reaction of proline to 1-pyrroline-5-carboxylate (P5C). P5C undergoes a non-enzymatic hydrolysis to glutamate semialdehyde (GSA), which is oxidized to glutamate by a NAD+- dependent enzyme P5CDH. PRODH and P5CDH are mono-functional enzymes in eukaryotes and Gram-positive bacteria; while in Gram-negative bacteria, the two enzymes are fused into one protein as two domains, known as proline utilization A (PutA). This dissertation work involved structural and functional studies of PRODH, P5CDH, PutA, and human aldehyde dehydrogenases (ALDHs). The results illuminated the substrate recognition for mono-functional PRODH and hot spot oligomerization mechanism for mono-functional P5CDH, also, demonstrated that diethylaminobenzaldehyde (DEAB) is a mechanism based inactivator for aldehyde dehydrogenase 7A1. Furthermore, the C-terminal domain found in PutAs, the only domain without any structural and functional information has been structurally and biochemically characterized.
Rapid Reaction Kinetics of Proline Dehydrogenase in the Multifunctional Proline Utilization A Protein