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Heme oxygenase (EC 1.14.99.3) (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.

May 2004 / Text revised.

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

HEME_OXYGENASE, PS00593; Heme oxygenase signature  (PATTERN)

Consensus pattern: L-[IV]-A-H-[STACH]-Y-[STV]-[RT]-Y-[LIVM]-G H is the heme-binding ligand Sequences known to belong to this class detected by the pattern: ALL Other sequence(s) detected in Swiss-Prot: NONE

• Retrieve an alignment of Swiss-Prot true positive hits:   Clustal format, color, condensed view  / Clustal format, color  / Clustal format, plain text  / Fasta format • Retrieve the sequence logo from the alignment • Taxonomic tree view of all Swiss-Prot/TrEMBL entries matching PS00593 • Retrieve a list of all Swiss-Prot/TrEMBL entries matching PS00593 • Scan Swiss-Prot/TrEMBL entries against PS00593 • view ligand binding statistics

Matching PDB structures: 1DVE 1DVG 1IRM 1IVJ ... [ALL]

1	Authors	Maines M.D.
	Title	Heme oxygenase: function, multiplicity, regulatory mechanisms, and clinical applications.
	Source	FASEB J. 2:2557-2568(1988).
	PubMed ID	3290025

2	Authors	Barinaga M.
	Title	Carbon monoxide: killer to brain messenger in one step.
	Source	Science 259:309-309(1993).
	PubMed ID	8093563

3	Authors	Richaud C., Zabulon G.
	Title	The heme oxygenase gene (pbsA) in the red alga Rhodella violacea is discontinuous and transcriptionally activated during iron limitation.
	Source	Proc. Natl. Acad. Sci. U.S.A. 94:11736-11741(1997).
	PubMed ID	9326680

4	Authors	Schmitt M.P.
	Title	Utilization 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.
	Source	J. Bacteriol. 179:838-845(1997).
	PubMed ID	9006041

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