Some properties of the cyanocobalamin-protein complex from sow's milk, and the mode of linkage of cyanocobalamin with protein

Abstract

Chemical examination of the cyanocobalamin-protein complex isolated from sow''s milk whey has shown that it contains 16.1% N, 7% carbohydrate and 9% hexosamine. Its amino acid com-position is typical of proteins, except for a high tyrosine content. The absorption curve of the complex in aqueous solution has peaks at 278 m/x (due to protein) and at 362, 410, 520 and 550 mfx (due to cyanocobalamin). The cyanocobalamin content of the complex is 23.6 /xg/mg, calculated from the absorption curve, and 22.4 Mg/mg measured by Escherichia coli. Using these figures, and assuming that one molecule of protein com-bines with one molecule of cyanocobalamin a molecular weight of 55,000 was deduced for the protein. The use of specific reagents to block different groups on the protein molecule, has shown that either a phenolic or an animo group on the protein may be concerned in its combination with the vitamin. The point at which the protein attaches itself to the cyanocobalamin molecule is also discussed.