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Haptocorrin serum

After the stomach s acidic environment facilitates the breakdown of vitamin B12 bound to food, the vitamin B12 binds to the intrinsic factor released by the stomach s parietal cells. The secretion of intrinsic factor generally corresponds to the release of hydrochloric acid and serves as a cell-directed carrier protein similar to transferrin for iron. This complex, resistant to degradation, forms in the duodenum and allows for subsequent absorption of vitamin B12 in the terminal ileum. The cobalamin-intrinsic factor complex is taken up into the ileal mucosal cell, the intrinsic factor is discarded, and the cobalamin is transferred to transcobalamin It, which serves as a transport protein. This complex is secreted into the circulation and is taken up by the fiver, bone marrow, and other cells. Transcobalamin 11 has a short half-fife of 1 hour and is rapidly cleared from the blood. Consequently, most circulating cobalamin is bound to serum haptocorrins (formerly transcobalamin I and transcobalamin IB) whose function is unknown. However, it should be noted that an alternate pathway for vitamin B12 absorption independent of intrinsic factor or an intact ter-... [Pg.1819]

The total amount of cobalamin present in serum is in the magnitude of 400pmol/L. Circulating cobalamins are bound to two proteins. Transcobala-min (TC) carries approximately 20% of the cobalamins in serum and the protein haptocorrin (HC) carries the remaining 80% (Nexo and Andersen 1977). In contrast, the amount of unsaturated (apo) transcobalamin is high compared with that of haptocorrin (Figure 26.1). [Pg.452]

Three Automated Platforms Reacts Differently Towards Changes in Sample Type. This section describes the design of assays for cobalamin from the three main players in automated cobalamin analysis on human serum (Abbott, Bayer Diagnostics and Roche) and demonstrates how these assays react if employed for the measurement of cobalamin in human milk. Human milk contains up to 200-fold more haptocorrin than serum and most of it is unsaturated with cobalamin. If haptocorrin is insufficiently denatured, it can interfere in the assays (Lildballe et al. 2009). [Pg.460]

We discovered these analytical problems when seeking to analyse the content of cobalamin in human milk (Lildballe et al. 2009). However, we encountered the same problem for serum samples with a high content of unsaturated haptocorrin (Lildballe et al. 2011). Once such a problem is realized, it is possible to... [Pg.460]

Serum cobalamin consists of picomolar amounts of several forms of the vitamin bound to transcobalamin or haptocorrin. [Pg.465]

Measurement of serum cobalamin includes release of cobalamin from its binding proteins transcobalamin and haptocorrin, conversion of the various forms of cobalamin into one form of the vitamin, and quantification employing microbiological or protein binding assays. [Pg.465]

Cobalamin analogues Cobalamin analogues are cobalamin-related molecules not able to act as coenzymes for the cobalamin dependent human enzymes. In serum, both cobalamin and cobalamin analogues are present. The protein transcobalamin can only bind active forms of cobalamin, whereas the protein haptocorrin can bind both cobalamins and analogues. [Pg.466]

Hardlei, T.F., and Nexo, E., 2009. A new principle for measurement of cobalamin and corrinoids, used for studies of cobalamin analogs on serum haptocorrin. Clinical Chemistry. 55 1002-1010. [Pg.468]


See other pages where Haptocorrin serum is mentioned: [Pg.1813]    [Pg.1820]    [Pg.453]    [Pg.461]    [Pg.497]   
See also in sourсe #XX -- [ Pg.420 , Pg.421 , Pg.465 ]




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Haptocorrin

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