The Molecular Size of Human Intrinsic Factor in Gastric Juice

Abstract

Stokes radius for human intrinsic factor in complex with ⁵⁷Co-cyano-cobalamin has been determined by Sephadex G-200 gel filtration. The experimental conditions were planned so as to simulate those occurring in the stomach: gel filtration was performed at 37° C and the mobile phase was gastric juice, pH 1.7 or pH 7. When amounts of intrinsic factor-bound vitamin B₁₂ similar to the mean concentrations occurring in vivo are studied, the Stokes radius is 3.3 nm. From this value and data from the literature a molecular mass of 57,000 daltons can be calculated. It is concluded that human intrinsic factor occurs in the monomer form in gastric juice.

Key Words:

• Cobalamins
• gel filtration
• intrinsic factor
• molecular mass
• Stokes radius
• vitamin B₁₂