Serum B12 binding proteins versus seminal plasma binder.

It was well confirmed that B12 binding protein in human serum and body fluids largely consists of two kinds of binding proteins, physiologically B12 transporting transcobalamin and haptocorrins which does not involve in B12 transport. In seminal plasma, very potent B12 binding protein, in quantity as much as 23 times of normal serum, was identified. Separation characteristics, gel filtration, CM cellulose column chromatography and column IEF all agreed as one of the haptocorrins. One peculiar feature of seminal plasma binder is marked heterogeneity of much lower pI regions suggesting the presence of increased amount of sialic residues on the molecule. The preliminary data from this laboratory support the view, however, physiological role such as the relationship to the spermatogenesis is not known. The most recent findings in clinical observation on B12 is the treatment of male infertility using methycobalamin. The detailed analysis of seminal binders may open up new arena of B12 bioeffect.