Analytical studies on cobalamin-binding proteins of human seminal plasma

• Published in: SEIBUTSU BUTSURI KAGAKU Vol. 38; no. 1; pp. 37 - 45
• Main Authors: Terada, Shoki, Yamada, Shoji, Inaba, Mizue, Fukuda, Morimichi
• Format: Journal Article
• Language: English
• Published: Japanese Electrophoresis Society 1994
• Subjects: cobalamin (vitamin B12)-binders; haptocorrin; human; isoelectrofocusing; seminal plasma
• ISSN: 0031-9082; 1349-9785
• DOI: 10.2198/sbk.38.37

Cobalamin-binding capacity of human seminal plasma amounted on average, to 23pmol/ml which was 20 times larger than that of serum. Most of the binding capacity was, in contrast to serum, unsaturated. Cobalamin-binders of seminal plasma separated into two distinct peaks on gel filtration; their elution positions and reactivity with antisera revealed that the largest portion of binding capacity is attributable to haptocorrin and the smaller portion to transcobalamin respectively. Total cobalamin-binding capacity and the ratio haptocorrin to transcobalamin varied significantly among samples examined. On column isoelectrofocusing, major peaks were seen at pH4.7 and 6.6; the former peak corresponding to 121 kDa reacted with an antihaptocorrin serum. One peculiar feature of the cobalamin-binder in seminal plasma is marked heterogeneity of components with pI below 4 as observed by the modified agarose-gel isoelectrofocusing technique. This suggested the presence of increased amounts of sialic acid residues on the binder molecule. The physiological role of cobalamin-binders in seminal plasma, such as the relationship to spermatogenesis, is still largely unknown. Detailed analysis of the binder may open up a new arena of cobalamin bioeffects.