The AKR1D1 gene was mapped to 7q33 chromosome, where it encodes an enzyme of 326 amino acids. This enzyme catalyzes the reduction of progesterone, androstenedione, 17-alpha-hydroxyprogesterone, and testosterone to 5-beta-reduced metabolites carrying a delta(4)-3-one structure.
Defects in this enzyme are the cause of congenital bile acid synthesis defect 2 (CBAS2), a disease characterized by jaundice, intrahepatic cholestasis and hepatic failure.