D-bifunctional protein (DBP), also known as peroxisomal multifunctional enzyme type 2 (MFP-2), as well as 17β-hydroxysteroid dehydrogenase type IV (17β-HSD type IV) is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
that in humans is encoded by the ''HSD17B4''
gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
.
It's an
alcohol oxidoreductase, specifically
17β-Hydroxysteroid dehydrogenase
A hydroxysteroid is a molecule derived from a steroid with a hydrogen replaced with a hydroxy group. When the hydroxy group is specifically at the C3 position, hydroxysteroids are referred to as sterols, with an example being cholesterol.
See ...
. It is involved in
fatty acid
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...
β-oxidation
In biochemistry and metabolism, beta-oxidation is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the mitochondria in eukaryotes to generate acetyl-CoA, which enters the citric acid cycl ...
and
steroid metabolism
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run c ...
(cf.
steroidogenesis
A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and ...
).
Function
The HSD17B4 gene encodes an enzyme involved in peroxisomal fatty acid beta-oxidation. It was first identified as a 17-beta-estradiol dehydrogenase (Leenders et al., 1996; van Grunsven et al., 1998). Peroxisomal beta-oxidation of fatty acids, originally described by Lazarow and de Duve (1976), is catalyzed by 3 enzymes:
acyl-CoA oxidase (see, e.g.,
ACOX1, MIM 609751); the 'D-bifunctional enzyme,' with
enoyl-CoA hydratase
Enoyl-CoA hydratase (ECH) or crotonase is an enzyme that hydrates the double bond between the second and third carbons on 2-trans/cis-enoyl-CoA:
ECH is essential to metabolizing fatty acids in beta oxidation to produce both acetyl CoA and e ...
and
D-3-hydroxyacyl-CoA dehydrogenase activity, and
3-ketoacyl-CoA thiolase
Thiolases, also known as acetyl-coenzyme A acetyltransferases (ACAT), are enzymes which convert two units of acetyl-CoA to acetoacetyl CoA in the mevalonate pathway.
Thiolases are ubiquitous enzymes that have key roles in many vital biochemi ...
(MIM 604054).
See also the L-bifunctional peroxisomal protein (
EHHADH; MIM 607037). The D- and L-bifunctional proteins have different substrate specificities. The D-bifunctional protein catalyzes the formation of 3-ketoacyl-CoA intermediates from both straight-chain and 2-methyl-branched-chain fatty acids and also acts in shortening cholesterol for bile acid formation. In contrast, the L-specific bifunctional protein does not have the latter 2 activities (Jiang et al., 1997).
upplied by OMIMref name="entrez">
See also
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D-bifunctional protein deficiency
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Perrault syndrome
References
Further reading
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