In enzymology, gluconate 5-dehydrogenase () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are D-gluconic acid and oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>). Its products are 5-oxo-D-gluconic acid, reduced NADH, and a proton. The enzyme can use nicotinamide adenine dinucleotide phosphate as an alternative cofactor.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD<sup>+</sup> or NADP<sup>+</sup> as acceptor. The systematic name of this enzyme class is D-gluconate:NAD(P)<sup>+</sup> 5-oxidoreductase. Other names in common use include 5-keto-D-gluconate 5-reductase, 5-keto-D-gluconate 5-reductase, 5-ketogluconate 5-reductase, 5-ketogluconate reductase, and 5-keto-D-gluconate reductase.
As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code .