American Journal of Clinical Nutrition, Vol 35, 1391-1399, Copyright © 1982 by The American Society for Clinical Nutrition, Inc

ORIGINAL RESEARCH COMMUNICATIONS

Metabolism of pyridoxine and protein binding of the metabolites in human erythrocytes

ML Fonda and CW Harker

The uptake, distribution, and metabolism of pyridoxine in human erythrocytes were determined by incubating isolated erythrocytes in isotonic sodium phosphate, pH 7.4, with [3H]pyridoxine. After 60 min at 37 degrees C, the erythrocytes had taken up approximately 80% of the radioactivity. At least 99% of the radioactivity in the erythrocytes was in the supernatant fraction of the cells and nearly 80% of that radioactivity was in pyridoxal-phosphate and was protein bound. The B6- protein complex was stabilized by reduction with borohydride. To identify the protein to which the radioactive B6 was bound, the hemolysate supernatant was fractionated by chromatography on DEAE Sephadex and carboxy methyl-cellulose. The protein fractions containing radioactivity were analyzed further by chromatography on Sephadex G- 150. Most of the radioactive B6 was found to Hb. Thus human erythrocytes rapidly took up pyridoxine and converted it to pyridoxal- phosphate. Much of the newly synthesized pyridoxal phosphate was bound to Hb.