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alpha-1 Microglobulin |
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| α1-Microglobulin (protein HC) is a lipocalin with immunosuppressive properties. The lipocalins are a family of proteins which transport small hydrophobic molecules such as steroids, bilins, retinoids, and lipids. Well known lipocalins are α1-microglobulin, alpha-1-acid glycoprotein (orosomucoid), apolipoprotein D, beta-lactoglobulin, and complement component C8 gamma chain etc. A gene in the lipocalin cluster encodes α1-microglobulin together with a Kunitz-type proteinase inhibitor, bikunin. The gene is translated into the α1-microglobulin-bikunin precursor, which is subsequently cleaved and the two proteins secreted to the blood separately.
α1-Microglobulin, is a monomeric protein of a molecular size of 27 kDa. It is produced by the liver and circulates in a free form, but is also bound in complexes to high molecular weight molecules. In human plasma, approx. 50% of α1-microglobulin forms a one-to-one complex with monomeric immunoglobulin A (IgA) by a reduction resistant bond.
Normal urine contains very small amounts of α1-microglobulin. In conditions with disturbed tubular function, reabsorption of α1-microglobulin is reduced and increased amounts are found in urine. Urinary α1-microglobulin seems a promising marker for renal abnormalities and for the differentiation of various nephrological and urological pathologies. |
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1) Penders J and Delanghe JR, 2004, Clin Chim Acta. 346(2):107-118.
2) Bo Åkerström et al., 2000, Biochim Biophys Acta. 1482(1-2):172-184.
3) Xu S and Venge P, 2000, Biochim Biophys Acta. 1482(1-2):298-307.
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