AKR1C1 also known as Aldo-keto reductase family 1 member C1, is member of the aldo/keto reductase superfamily, which consists of more than 40 known enzymes and proteins. These enzymes catalyze the conversion of aldehydes and ketones to their corresponding alcohols by utilizing NADH and/or NADPH as cofactors. The enzymes display overlapping but distinct substrate specificity. This enzyme catalyzes the reduction of progesterone to the inactive form 20-alpha-hydroxy-progesterone. Recombinant human AKR1C1 protein was expressed in E.coli and purified by using conventional chromatography techniques.