Cytochrome-''b''
5 reductase is a
NADH
Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an aden ...
-dependent
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
that converts ferricytochrome from a Fe3+ form to a Fe2+ form.
It contains
FAD
A fad or trend is any form of collective behavior that develops within a culture, a generation or social group in which a group of people enthusiastically follow an impulse for a short period.
Fads are objects or behaviors that achieve short- ...
and catalyzes the reaction:
In its b5-reducing capacity, this enzyme is involved in desaturation and elongation of fatty acids, cholesterol biosynthesis, and drug metabolism.
This enzyme can also reduce
methemoglobin
Methemoglobin (British: methaemoglobin) (pronounced "met-hemoglobin") is a hemoglobin ''in the form of metalloprotein'', in which the iron in the heme group is in the Fe3+ (ferric) state, not the Fe2+ (ferrous) of normal hemoglobin. Sometimes, it i ...
to normal
hemoglobin
Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyte ...
, gaining it the inaccurate synonym methemoglobin reductase. Isoforms expressed in
erythrocyte
Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...
s (CYB5R1, CYB5R3) perform this function ''in vivo''. Ferricyanide is another substrate ''in vitro''.
The following four human genes encode cytochrome-''b''
5 reductases:
*
CYB5R1
NADH-cytochrome b5 reductase 1 is an enzyme that in humans is encoded by the ''CYB5R1'' gene.
Structure
The CYB5R1 gene is located on the 1st chromosome, with its specific location being 1q32.1. The gene contains 9 exons. CYB5R1 encodes a 34.1 ...
*
CYB5R2
Cytochrome b5 reductase 2 is an enzyme that in humans is encoded by the ''CYB5R2'' gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' o ...
*
CYB5R3
NADH-cytochrome b5 reductase 3 is an enzyme that in humans is encoded by the ''CYB5R3'' gene.
Structure
The CYB5R3 gene is located on the 22nd chromosome, with its specific location being 22q13.2. The gene contains 12 exons. CYB5R3 encodes a 34.2 ...
*
CYB5R4
Cytochrome b5 reductase 4 is an enzyme that in humans is encoded by the ''CYB5R4'' gene.
NCB5OR is a flavohemoprotein that contains functional domains found in both cytochrome
Cytochromes are redox-active proteins containing a heme, with a cent ...
*
CYB5RL
See also
*
Cytochrome b5
Cytochromes ''b''5 are ubiquitous electron transport hemoproteins found in animals, plants, fungi and purple phototrophic bacteria. The microsomal and mitochondrial variants are membrane-bound, while bacterial and those from erythrocytes and ot ...
*
Diaphorase Diaphorase may refer to:
* Cytochrome b5 reductase, an enzyme
* NADH dehydrogenase, an enzyme
* NADPH dehydrogenase
In enzymology, a NADPH dehydrogenase () is an enzyme that catalysis, catalyzes the chemical reaction
:NADPH + H+ + acceptor \right ...
*
Methemoglobinemia
*
Reductase
*
Leghemoglobin reductase
References
External links
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EC 1.6.2