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In vivo Plasma Binding Capacity for Cyanocobalamin *
Author(s) -
Schiffer L. M.,
Cronkite E. P.,
Meyer L. M.,
Miller I. F.
Publication year - 1966
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1111/j.1365-2141.1966.tb00140.x
Subject(s) - cyanocobalamin , in vivo , vitamin b12 , chemistry , blood proteins , plasma protein binding , in vitro , globulin , biochemistry , endocrinology , biology , microbiology and biotechnology
M any investigators have alluded to or described the presence of multiple vitamin B 12 binding proteins in human plasma (Mendelsohn, Watkin, Horbett and Fahey, 1958; Miller, 1958; Hall and Finkler, 1962; Rosenthal, Hill and Haessler, 1964; Heller, Epstein, Cunningham, Henderson and Yakulis, 1964). Recently, Hall and Finkler (1963, 1964) separated two cyanocobalamin plasma binders with distinctly different characteristics. One fraction (Transcobalamin II or TC II) is apparently a β‐globulin which is involved in the immediate carrier state, while the other (Transcobalamin I or TC I), an α‐globulin, is the endogenous B 12 binding protein. Gabuzda, Worm‐Petersen and Lous (1965) confirmed these findings, demonstrating that cyanocobalamin is bound in vitro by a distinctly separate protein from that to which it is bound endogenously. Methods derived from a study of plasma binding by vitamin B 12 analogues have been utilized to determine in vivo plasma binding capacity for cyanocobalamin (Meyer, Schiffer, White and Cronkite, 1965). It is proposed that this in vivo plasma binding capacity represents to a large extent the B 12 carrying capacity of TC II.