D-proline reductase catalyzes the reductive cleavage of a C-N bond in D-proline resulting in the formation of 5-aminovalerate. The alpha subunit has been shown to bind D-proline, presumably via the pyruvoyl group. 5-aminopentanoate + [PrdC protein]-Se-L-selenocysteinyl-S-L-cysteine = [PrdC protein]-L-selenocysteine/L-cysteine + D-proline Consists of 3 subunits of 23, 26 and 45 kDa (alpha, gamma and beta respectively). The molecular weight of the complex is approximately 870 kDa, suggesting a decameric structure, if all 3 subunits are present in equal stoichiometry. The peptide chain is cleaved into beta and alpha chains, and the alpha chain N-terminal cysteine is deaminated and oxidized to form a reactive pyruvoyl group. The reaction mechanism first involves the formation of an adduct (and not a Schiff base) between the nitrogen of proline and the pyruvoyl group of the alpha subunit. The selenol anion of selenocysteine in PrdB nucleophilically attacks the alpha-carbon, resulting in cleavage of the N-C bond of the proline ring. This intermediate is then transformed to the oxidized gamma subunit containing a mixed selenide/sulfide group and to the 5-aminovalerate adduct of the alpha subunit. The final product, 5-aminovalerate, is formed by hydrolysis. Subsequently, the selenide-sulfide group of PrdB is reduced, but the natural electron donating system for D-proline reductase is unknown.