May function in the pulmonary metabolism of endogenous carbonyl compounds, such as aliphatic aldehydes and ketones derived from lipid peroxidation, 3-ketosteroids and fatty aldehydes, as well as in xenobiotic metabolism. a secondary alcohol + NADP(+) = a ketone + H(+) + NADPH Homotetramer. Predominantly expressed in lung, in ciliated cells, non-ciliated bronchiolar cells and type-II alveolar pneumocytes (PubMed:7705352, PubMed:8040004). Also detected in adipose tissue (at protein level) (PubMed:7705352). Low expression in testis, heart, kidney, spleen, brain and liver (PubMed:7705352). By glucocorticoids. Activated by fatty acids. Uses both NADP and NAD as substrates. Has a strong preference for NADP. Belongs to the short-chain dehydrogenases/reductases (SDR) family.