7my9
Structure of proline utilization A with 1,3-dithiolane-2-carboxylate bound in the proline dehydrogenase active site
Structural highlights
FunctionF7X6I3_SINMM Oxidizes proline to glutamate for use as a carbon and nitrogen source.[PIRNR:PIRNR000197] Publication Abstract from PubMedProline dehydrogenase (PRODH) is a flavoenzyme that catalyzes the first step of proline catabolism, the oxidation of l-proline to Delta(1)-pyrroline-5-carboxylate. PRODH has emerged as a cancer therapy target because of its involvement in the metabolic reprogramming of cancer cells. Here, we report the discovery of a new class of PRODH inactivator, which covalently and irreversibly modifies the FAD in a light-dependent manner. Two examples, 1,3-dithiolane-2-carboxylate and tetrahydrothiophene-2-carboxylate, have been characterized using X-ray crystallography (1.52-1.85 A resolution), absorbance spectroscopy, and enzyme kinetics. The structures reveal that in the dark, these compounds function as classical reversible, proline analogue inhibitors. However, exposure of enzyme-inhibitor cocrystals to bright white light induces decarboxylation of the inhibitor and covalent attachment of the residual S-heterocycle to the FAD N5 atom, locking the cofactor into a reduced, inactive state. Spectroscopic measurements of the inactivation process in solution confirm the requirement for light and show that blue light is preferred. Enzyme activity assays show that the rate of inactivation is enhanced by light and that the inactivation is irreversible. We also demonstrate the photosensitivity of cancer cells to one of these compounds. A possible mechanism is proposed involving photoexcitation of the FAD, while the inhibitor is noncovalently bound in the active site, followed by electron transfer, decarboxylation, and radical combination steps. Our results could lead to the development of photopharmacological drugs targeting PRODH. Photoinduced Covalent Irreversible Inactivation of Proline Dehydrogenase by S-Heterocycles.,Campbell AC, Prater AR, Bogner AN, Quinn TP, Gates KS, Becker DF, Tanner JJ ACS Chem Biol. 2021 Sep 20. doi: 10.1021/acschembio.1c00427. PMID:34542291[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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