Clearance of heme in mammals is a two step process starting with conversion of heme to biliverdin by heme oxygenase, followed by reduction of biliverdin to bilirubin by bilivredin reductase. Biliverdin IX b reductase (BLVRB) converts the B isomer of biliverdin IX to bilirubin IX b, which constitutes 87% of total bilirubin in fetal bile. Therefore BLVRB is especially important for fetal heme metabolism and clearance. BLVRB is a cytoplasmic enzyme expressed at high levels in erythrocytes and liver, but is present in other tissues. The enzyme is identical to flavin reductase, which is an oxidoreductase that catalyses the NADPH-dependent reduction for a variety of flavins, such as riboflavin, FAD or FMN and methemoglobin. BLVRB is structurally distinct from BLVRA. In contrast to BLVRA, which prefers the biliverdin a isomer but could also use the B isomer as substrate, BLVRB is specific for the B isomer.
Intended for research use only. Not for use in human, therapeutic, or diagnostic applications.