In human liver cytosolic fractions, four forms of biliverdin reductase have been identified, including two biliverdin-IX Beta reductases and two biliverdin-IX Alpha reductases, designated isozymes I and II and isozymes III and IV, respectively. Biliverdin reductase A (BLVRA), also designated biliverdin-IX Alpha-reductase, belongs to the GFO/iIDH/MocA family and the biliverdin reductase subfamily. The gene that encodes this cytoplasmic protein maps to chromosome 7p14-cen. BLVRA reduces biliverdin IX ?(the ?methene bridge of the open tetrapyrrole) to bilirubin with the concomitant oxidation of an NADH or NADPH cofactor (bilirubin + NADP+ = biliverdin + NADPH). BLVRA is expressed primarily in liver.