Dehydrogenase that mediates the formation of 2,5-dihydroxybenzoic acid (2,5-DHBA), a siderophore that shares structural similarities with bacterial enterobactin and associates with lcn2, thereby playing a key role in iron assimilation and homeostasis (By similarity). Also acts as a 3-hydroxybutyrate dehydrogenase (By similarity). (R)-3-hydroxybutanoate + NAD(+) = acetoacetate + H(+) + NADH Siderophore biosynthesis. Homotetramer. Belongs to the short-chain dehydrogenases/reductases (SDR) family.