PROSITE documentation PDOC00512
Heme oxygenase signature


Heme oxygenase (EC (HO) [1] is the microsomal enzyme that, in animals, carries out the oxidation of heme, it cleaves the heme ring at the α methene bridge to form biliverdin and carbon monoxide. Biliverdin is subsequently converted to bilirubin by biliverdin reductase.

In mammals there are three isozymes of heme oxygenase: HO-1 to HO-3. The first two isozymes differ in their tissue expression and their inducibility: HO-1 is highly inducible by its substrate heme and by various non-heme substances, while HO-2 is non-inducible. It has been suggested [2] that HO-2 could be implicated in the production of carbon monoxide in the brain where it is said to act as a neurotransmitter.

In the genome of the chloroplast of red algae as well as in cyanobacteria, there is a heme oxygenase (gene pbsA) that is the key enzyme in the synthesis of the chromophoric part of the photosynthetic antennae [3]. An heme oxygenase is also present in the bacteria Corynebacterium diphtheriae (gene hmuO), where it is involved in the acquisition of iron from the host heme [4].

There is, in the central section of these enzymes, a well conserved region centered on a histidine residue. We have used this region as a signature pattern.

Last update:

May 2004 / Text revised.


Technical section

PROSITE method (with tools and information) covered by this documentation:

HEME_OXYGENASE, PS00593; Heme oxygenase signature  (PATTERN)


1AuthorsMaines M.D.
TitleHeme oxygenase: function, multiplicity, regulatory mechanisms, and clinical applications.
SourceFASEB J. 2:2557-2568(1988).
PubMed ID3290025

2AuthorsBarinaga M.
TitleCarbon monoxide: killer to brain messenger in one step.
SourceScience 259:309-309(1993).
PubMed ID8093563

3AuthorsRichaud C. Zabulon G.
TitleThe heme oxygenase gene (pbsA) in the red alga Rhodella violacea is discontinuous and transcriptionally activated during iron limitation.
SourceProc. Natl. Acad. Sci. U.S.A. 94:11736-11741(1997).
PubMed ID9326680

4AuthorsSchmitt M.P.
TitleUtilization of host iron sources by Corynebacterium diphtheriae: identification of a gene whose product is homologous to eukaryotic heme oxygenases and is required for acquisition of iron from heme and hemoglobin.
SourceJ. Bacteriol. 179:838-845(1997).
PubMed ID9006041

PROSITE is copyrighted by the SIB Swiss Institute of Bioinformatics and distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives (CC BY-NC-ND 4.0) License, see prosite_license.html.


View entry in original PROSITE document format
View entry in raw text format (no links)