Intrinsic Factor (IF), transcobalamin (TC) and haptocorrin (HC) are the three binding proteins involved in the assimilation and transport of vitamin B12. These binding proteins ensure the efficient up-take of the very small amounts of dietary vitamin B12.  All of these proteins have extremely high affinity for vitamin B12 (dissociation constants lower than 1pM) (1).

When transcobalamin and haptocorrin bind vitamin B12 the resulting complexes are known as holotranscobalamin (Active-B12 or holoTC) and holohaptocorrin (holoHC) to distinguish them from the proteins carrying no vitamin.

Active-B12 is the form of vitamin B12 that is taken up by cells in the body and is the minor (approximately 25%) fraction of circulating vitamin B12.

1. Fedosov SN et al., J Biol Chem., 2002; 277: 9989-9996.

News

Coming Soon !  The full video recording of the Euromedlab 2007 Active B12 workshop will be available in the next few weeks, register for your copy.

Live CME Web Conference on vitamin B12 deficiency, Prof. Ralph Green, Dec 13th 2007, register now.

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Meetings

8-11 December, 2007
American Society of Hematology, Atlanta, booth 544
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