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Vitamin B12 binders (transcobalamins) in serum.
Crit Rev Clin Lab Sci. 1982; 18(1):1-30.CR

Abstract

The measurement of plasma or serum vitamin B12 (B12) binders is important in the diagnosis of congenital megaloblastic anemias, the myeloproliferative disorders and perhaps in other malignancies. Two classes of binders circulate in plasma, Transcobalamin II (TC II) and R-binders. The latter have been divided by some authors into transcobalamin I (TC I) and transcobalamin III (TC III), and the validity of this division is discussed. R-binders and TC II differ in their apparent molecular weight on gel filtration chromatography, by which method they can be separated reliably. However, the technique is time-consuming and cumbersome and a variety of rapid separation methods have been described in the literature. These are discussed and compared to the standard gel filtration separation method. TC I and III are separable on the basis of their differing charges, and the methods which have been described for accomplishing this are compared and critically reviewed. There has been some controversy in the literature as to whether plasma or serum should be used to measure circulating B12 binders. Leukocytes, which contain R-binders, release these in vitro and this release is greatest when blood is allowed to clot and the serum separated. Consequently, the use of plasma, sometimes with agents added to prevent leukocytic release of binder, has been advocated. Yet, none of the agents used eliminates artifact totally, and this aspect, too, is reviewed. Lastly, several techniques for the purification of B12 binders have been described. Some techniques result in pure binder preparations, while others result in preparations which are free of other binders but contaminated with non-B12 binding proteins. Both approaches have advantages and disadvantages, and these are discussed.

Authors

No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Review

Language

eng

PubMed ID

6295699

Citation

Fernandes-Costa, F, and J Metz. "Vitamin B12 Binders (transcobalamins) in Serum." Critical Reviews in Clinical Laboratory Sciences, vol. 18, no. 1, 1982, pp. 1-30.
Fernandes-Costa F, Metz J. Vitamin B12 binders (transcobalamins) in serum. Crit Rev Clin Lab Sci. 1982;18(1):1-30.
Fernandes-Costa, F., & Metz, J. (1982). Vitamin B12 binders (transcobalamins) in serum. Critical Reviews in Clinical Laboratory Sciences, 18(1), 1-30.
Fernandes-Costa F, Metz J. Vitamin B12 Binders (transcobalamins) in Serum. Crit Rev Clin Lab Sci. 1982;18(1):1-30. PubMed PMID: 6295699.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Vitamin B12 binders (transcobalamins) in serum. AU - Fernandes-Costa,F, AU - Metz,J, PY - 1982/1/1/pubmed PY - 1982/1/1/medline PY - 1982/1/1/entrez SP - 1 EP - 30 JF - Critical reviews in clinical laboratory sciences JO - Crit Rev Clin Lab Sci VL - 18 IS - 1 N2 - The measurement of plasma or serum vitamin B12 (B12) binders is important in the diagnosis of congenital megaloblastic anemias, the myeloproliferative disorders and perhaps in other malignancies. Two classes of binders circulate in plasma, Transcobalamin II (TC II) and R-binders. The latter have been divided by some authors into transcobalamin I (TC I) and transcobalamin III (TC III), and the validity of this division is discussed. R-binders and TC II differ in their apparent molecular weight on gel filtration chromatography, by which method they can be separated reliably. However, the technique is time-consuming and cumbersome and a variety of rapid separation methods have been described in the literature. These are discussed and compared to the standard gel filtration separation method. TC I and III are separable on the basis of their differing charges, and the methods which have been described for accomplishing this are compared and critically reviewed. There has been some controversy in the literature as to whether plasma or serum should be used to measure circulating B12 binders. Leukocytes, which contain R-binders, release these in vitro and this release is greatest when blood is allowed to clot and the serum separated. Consequently, the use of plasma, sometimes with agents added to prevent leukocytic release of binder, has been advocated. Yet, none of the agents used eliminates artifact totally, and this aspect, too, is reviewed. Lastly, several techniques for the purification of B12 binders have been described. Some techniques result in pure binder preparations, while others result in preparations which are free of other binders but contaminated with non-B12 binding proteins. Both approaches have advantages and disadvantages, and these are discussed. SN - 1040-8363 UR - https://www.unboundmedicine.com/medline/citation/6295699/Vitamin_B12_binders__transcobalamins__in_serum_ L2 - https://www.tandfonline.com/doi/full/10.3109/10408368209082588 DB - PRIME DP - Unbound Medicine ER -