Cleavage of heme b (Fe-protoporphyrin IX) at the a-methene carbon bridge to form the open tetrapyrrole, biliverdin IXa and carbon monoxide (CO) is catalyzed by heme oxygenase (HO) isozymes HO-1 and HO-2 (heme hydrogen-donor: oxygen oxidoreductase; EC 1.14.99.3). In mammalian species, biliverdin reductase (BVR; bilirubin: NAD(P)+ oxidoreductase; EC 1.3.1.24) converts the open tetrapyrrole to bilirubin. This pathway represents the only efficient way of making bilirubin and thereby deterring activation of oxygen by the heme molecule. HO-1 belongs to the heat shock protein family (Hsp32), while HO-2 takes a constitutive form expressed at exceedingly high levels in the brain and testes. The end products of the heme degradation process carry out important physiological activities. CO may act as a messenger in the brain and systemic organs stimulating cGMP-production through interactions with the heme-dependent form of guanylate cyclase. Bile pigments display potent antioxidant activity as well as effective antiviral activity against HIV and herpes virus. BVR is unique among all enzymes characterized to date in having two pH optima (6.8 and 8.7), using a different cofactor at each pH range (NADH at pH 7.0 and NADPH at pH 8.7). The enzyme displays pI and molecular mass microheterogeneity, apparently a result of post translational modifications. In rat, the enzyme also shows a tissue specific developmental pattern. BVR is not inactivated by heat shock, and its preexisting message is not sequestered from translation subsequent to thermal stress. Furthermore, reductase preserves microheterogeneity under thermal stress. BVR expression occurs not only in cells and brain regions that already display HO-1 and HO-2, but also in regions and cell types with potential to induce stress proteins. Rat cDNA for BVR has been isolated and characterized. The deduced protein contains 3 cysteine residues (Cys73, Cys281, and Cys290) involved in cofactor and substrate binding. Human BVR consists of a substantially longer polypeptide than the rat enzyme (41-42 kDa vs. 33 kDa), but also is dual cofactor and dual pH dependent, requires free SH groups for activity, and displays pI and molecular mass microheterogeneity. The human and rat BVR share some antigenic epitopes and show immunochemical cross reactivity.
- For Immunohistochemistry, Western Blot
Recognizes human, mouse, rat, hamster and pig Biliverdin Reductase. Detects bands of ~33kDa (rat) and ~41-42kDa (human) by Western blot.
Type: Primary
Antigen: BVR
Clonality: Polyclonal
Clone:
Conjugation:
Epitope:
Host: Rabbit
Isotype:
Reactivity: Human
