Alpha-1-microglobulin (A1M, α1-microglobulin,
[B. Ekström, P.A. Peterson, I. Berggård "A urinary and plasma alpha-1-glycoprotein of low molecular weight: isolation and some properties." ''Biochem. Biophys. Res. Commun'' 1975, vol.] sometimes also called Protein HC
) is a
microglobulin
Microglobulin is a globulin of relatively small molecular weight. It can be contrasted to macroglobulin.,
Examples include:
* Beta-2 microglobulin
* Alpha-1-microglobulin Alpha-1-microglobulin (A1M, α1-microglobulin,B. Ekström, P.A. Peterson, I. ...
, a small globular protein. It is found in all vertebrates, including humans, and is distributed in
blood plasma
Blood plasma is a light amber-colored liquid component of blood in which blood cells are absent, but contains proteins and other constituents of whole blood in suspension. It makes up about 55% of the body's total blood volume. It is the intra ...
and extravascular tissues of all organs. It is synthesized in most cells of the body, but mainly in the liver
[Alpha-1-microglobulin: Innate defence against pathological oxidation]
by Magnus G Olsson, 2009 from a gene that codes for the
alpha-1-microglobulin/bikunin precursor
Protein AMBP is a protein that in humans is encoded by the ''AMBP'' gene.
Interactions
Alpha-1-microglobulin/bikunin precursor has been shown to interact with CD79A.
See also
* Inter-alpha-trypsin inhibitor
* Alpha-1-microglobulin
Referen ...
.
Structure
Human A1M is composed of a 183-amino-acid peptide carrying three carbohydrate chains. It belongs to a protein family, the
lipocalins, all members of which are shaped as a basket built from eight beta-strands of the peptide chain. A cysteine residue on one of the loops at the open end of the basket is of central importance for the function.
Function
A1M binds and degrades
heme, is a
radical scavenger A scavenger in chemistry is a chemical substance added to a mixture in order to remove or de-activate impurities and unwanted reaction products, for example oxygen, to make sure that they will not cause any unfavorable reactions. Their use is wide- ...
as well as a
reductase
A reductase is an enzyme that catalyzes a reduction reaction.
Examples
* 5α-Reductase
* 5β-Reductase
* Dihydrofolate reductase
* HMG-CoA reductase
* Methemoglobin reductase
* Ribonucleotide reductase
* Thioredoxin reductase
* ''E. coli'' ...
. A model has been proposed in which A1M is described as a circulating “waste bin” which continuously removes free radicals and oxidizing agents, particularly heme, from the tissues. It is subsequently transported to the kidneys, where it is broken down. The protein is therefore believed to protect cells and tissues against the damage that is induced by abnormally high concentrations of free hemoglobin and/or
reactive oxygen species (also called “
oxidative stress”).
A1M is also immunoregulatory: the immune response of lymphocytes and neutrophils is partly suppressed by A1M.
Role in diagnosis
A1M can be used as an indicator of
proteinuria. The test can be regarded as positive when the ratio of A1M (in
milligram
The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially. ...
s) and creatinine in
millimoles
The mole, symbol mol, is the unit of amount of substance in the International System of Units (SI). The quantity amount of substance is a measure of how many elementary entities of a given substance are in an object or sample. The mole is define ...
in the urine is over 0.7 mg/mmol.
A test for
preeclampsia
Pre-eclampsia is a disorder of pregnancy characterized by the onset of high blood pressure and often a significant amount of protein in the urine. When it arises, the condition begins after 20 weeks of pregnancy. In severe cases of the disease ...
, where A1M serves as the diagnostic marker, has been proposed. It is based upon the fact that oxidative stress in the placenta tissue triggers the endogenous synthesis and plasma concentration of the protein.
Therapeutic potential
A1M is a candidate for a number of therapeutic applications which includes the treatment or alleviation of preeclampsia, tissue damage caused by bleeding in brain, and chronic leg ulcers.
References
{{reflist
Lipocalins