Heme oxygenase-1 (HO-1, encoded by the HMOX1 gene) catalyzes the oxidative degradation of heme to
biliverdin (BV), carbon monoxide, and ferrous iron.
Biliverdin is the product of heme degradation and has antioxidant and immunomodulating properties, supporting the possibility that if only a limited amount of
biliverdin can be produced, deposition of this pigment into eggshells may be costly to females.
While it has been suggested that the blue skeleton of Heliopora originated from
biliverdin IX[alpha] (Rudiger et al.
High concentrations of
biliverdin, say over 50 micromoles per liter, make humans sick with jaundice.
Hemeoxygenase-I is an enzyme that plays a role in the reduction of heme to
biliverdin, carbon monoxide, and free divalent iron.
Biliverdin reductase-A (BVR-A) is a pleiotropic enzyme that not only catalyzes the synthesis of the powerful antioxidant bilirubin but through its Ser/Thr/Tyr kinase activity modulates cell signaling networks including the two main arms of insulin signaling: MAPK and PI3K.
They involve converting conjugated bilirubin forms into
biliverdin and, unlike the diazo method, are unaffected by coexisting substances such as hemoglobin or vitamin C (6).
Bilirubin and
biliverdin protect rodents against diabetic nephropathy by downregulating NAD(P)H oxidase," Kidney International, vol.
Further breakdown releases
biliverdin (green) and finally, bilirubin (yellow).
HO- 1 is a rate limiting enzyme which is identified as inducible form and catabolises heme into three products: CO free iron and
biliverdin.
Bilirubin benefits: cellular protection by a
biliverdin reductase antioxidant cycle.
Biliverdin is oxidized to bilirubin, a highly antioxidative compound [52].
