Transcobalamins I and II as natural transport proteins of vitamin B12.

The Journal of Clinical Investigation
C A Hall

Abstract

There are two conflicting theories of how plasma vitamin B12 (B12) is transported in man: (a) by two distinct transport proteins, transcobalamins I and II (TC I and II), each having a specific role and time of function; and (b) by three active transport proteins, TC I, II, and III, that take up B12 randomly in proportion to the unsaturated amounts of each. To test these theories a man was given 1.12 mug, 229 muCi, of [57Co]B12 mixed with food. Blood samples were taken several times on the 1st day and at lengthening intervals up to day 51. The amount of TC II-B12 was measured in each sample by: gel filtration and by precipitation with (NH4)2SO4. Total serum R-B12 was then separated into TC I and TC III by: (a) a single step anion exchange system and (b) isoelectric focusing (IEF). As the B12 was being absorbed, 92-95% of that in venous blood was carried by TC II. Absolute and percentage transport by TC II declined sharply during the first 24 h; between days 7 and 51 20-33% of the label was on TC II, and the rest was carried by R-type binders. Absolute transport by TC I did not reach a maximum until after day 1 and before day 3. Transport by an alpha2 R-type binder, TC III, could not be demonstrated. TC I was isoelectrically hete...Continue Reading

References

Nov 1, 1974·The Journal of Pediatrics·W H HitzigD Vischer
Dec 1, 1973·British Journal of Haematology·J M EnglandI Chanarin
Dec 29, 1972·Biochimica Et Biophysica Acta·U H Stenman, R Gräsbeck
Jun 1, 1971·British Journal of Haematology·R J Harrison
Nov 18, 1971·The New England Journal of Medicine·N HakamiJ Lazerson
Oct 8, 1963·Biochimica Et Biophysica Acta·C A HALL, A E FINKLER

❮ Previous
Next ❯

Citations

Dec 1, 1989·Archives of Biochemistry and Biophysics·E Kukiełka, A I Cederbaum
Mar 15, 1988·Clinica Chimica Acta; International Journal of Clinical Chemistry·J van KapelJ Lindemans
Jan 1, 1983·Comparative Biochemistry and Physiology. B, Comparative Biochemistry·C R Kapadia, K Voloshin
Feb 19, 2013·Biochimie·Edward V Quadros, Jeffrey M Sequeira
Nov 1, 1982·The Journal of Pediatrics·D J NiebruggeC R Scott
Jun 23, 1977·The New England Journal of Medicine·R M DonaldsonD Serfilippi
Aug 2, 1984·The New England Journal of Medicine·F S RosenR J Wedgwood
Jan 1, 1976·Preparative Biochemistry·C R SavageC A Hall
Aug 17, 1999·Annual Review of Nutrition·B Seetharam
Jan 1, 1978·The Journal of Clinical Investigation·P Youngdahl-TurnerR H Allen
Oct 17, 2001·American Journal of Clinical Pathology·R CarmelZ Frouhar
Jan 1, 1985·Critical Reviews in Oncology/hematology·Y KanoF Takaku
Apr 1, 1976·Archives of Biochemistry and Biophysics·C R Savage, P D Green
Oct 1, 1976·Archives of Biochemistry and Biophysics·P D GreenC A Hall
Jan 1, 1982·Critical Reviews in Clinical Laboratory Sciences·F Fernandes-Costa, J Metz
Jul 1, 1989·Experimental Cell Research·C A Hall, P D Colligan
May 1, 1979·Journal of Dairy Science·D M PolakM Haluska
Jan 1, 1978·CRC Critical Reviews in Clinical Laboratory Sciences·L Kass
Nov 24, 2019·Journal of Veterinary Internal Medicine·Stefanie KatherRomy M Heilmann
Dec 1, 1977·Scandinavian Journal of Clinical and Laboratory Investigation·E Nexø, J Andersen
Oct 17, 2009·British Journal of Haematology·Edward V Quadros
Dec 1, 2010·Expert Reviews in Molecular Medicine·D Sean Froese, Roy A Gravel
Jul 13, 2013·The Journal of Biological Chemistry·Evelyne FurgerAndrea E Prota
Jul 1, 1987·Journal of the American Geriatrics Society·D L MarcusM L Freedman
Mar 1, 1976·Scandinavian Journal of Haematology·C A Hall
May 28, 2019·Journal of Assisted Reproduction and Genetics·Han Sung ParkNam Keun Kim
Jun 1, 1976·British Journal of Haematology·R H Allen
Nov 1, 1976·Scandinavian Journal of Clinical and Laboratory Investigation·P Gimsing, E Nexö
Oct 13, 1999·Journal of Inherited Metabolic Disease·H BibiD S Rosenblatt
Jun 15, 1977·Clinica Chimica Acta; International Journal of Clinical Chemistry·T A MorelliC A Hall

❮ Previous
Next ❯

Related Concepts

Trending Feeds

COVID-19

Coronaviruses encompass a large family of viruses that cause the common cold as well as more serious diseases, such as the ongoing outbreak of coronavirus disease 2019 (COVID-19; formally known as 2019-nCoV). Coronaviruses can spread from animals to humans; symptoms include fever, cough, shortness of breath, and breathing difficulties; in more severe cases, infection can lead to death. This feed covers recent research on COVID-19.

Blastomycosis

Blastomycosis fungal infections spread through inhaling Blastomyces dermatitidis spores. Discover the latest research on blastomycosis fungal infections here.

Nuclear Pore Complex in ALS/FTD

Alterations in nucleocytoplasmic transport, controlled by the nuclear pore complex, may be involved in the pathomechanism underlying multiple neurodegenerative diseases including Amyotrophic Lateral Sclerosis and Frontotemporal Dementia. Here is the latest research on the nuclear pore complex in ALS and FTD.

Applications of Molecular Barcoding

The concept of molecular barcoding is that each original DNA or RNA molecule is attached to a unique sequence barcode. Sequence reads having different barcodes represent different original molecules, while sequence reads having the same barcode are results of PCR duplication from one original molecule. Discover the latest research on molecular barcoding here.

Chronic Fatigue Syndrome

Chronic fatigue syndrome is a disease characterized by unexplained disabling fatigue; the pathology of which is incompletely understood. Discover the latest research on chronic fatigue syndrome here.

Evolution of Pluripotency

Pluripotency refers to the ability of a cell to develop into three primary germ cell layers of the embryo. This feed focuses on the mechanisms that underlie the evolution of pluripotency. Here is the latest research.

Position Effect Variegation

Position Effect Variagation occurs when a gene is inactivated due to its positioning near heterochromatic regions within a chromosome. Discover the latest research on Position Effect Variagation here.

STING Receptor Agonists

Stimulator of IFN genes (STING) are a group of transmembrane proteins that are involved in the induction of type I interferon that is important in the innate immune response. The stimulation of STING has been an active area of research in the treatment of cancer and infectious diseases. Here is the latest research on STING receptor agonists.

Microbicide

Microbicides are products that can be applied to vaginal or rectal mucosal surfaces with the goal of preventing, or at least significantly reducing, the transmission of sexually transmitted infections. Here is the latest research on microbicides.