An immunological and chromatographic comparison of human intrinsic factor and the acid-stable gastric esterase VI A.

When examined by immunoelectrophoresis and double-gel diffusion, gastric acid-stable esterase (VI A) and human intrinsic factor (IF) behaved as different substances. The VI A migrated in agar-gel electrophoresis mainly as a β/β-globulin and IF as β/α-globulin. Both showed overlapping migration and diffusion near the starting point. On DEAE-chromatography IF was eluted together with VI A at 0·05–0·075 M, pH 7·0. In gel filtration experiments with Sephadex G 100 and G 200, the IF from neutralized gastric juice (NGJ) and from gastric mucosa (GM) was eluted in a definite range according to its molecular weight of 60,000. No IF was found in acid gastric juice (AGJ). Two immunologically identical variants of VI A were eluted at two different ranges when NGJ and GM were used for gel filtration. The variant of VI A with the lower molecular weight was eluted together with IF. When AGJ was used, only the VI A with the higher molecular weight was found and in an elution range quite different from that for IF. Of the purified substances, only IF showed vitamin B binding, which could be inhibited by serum from a patient with pernicious anaemia, and only heteroimmune serum against this B-binding fraction contained IF antibodies of the blocking and binding types. IF and VI A proved to be biochemically and immunologically distinct proteins.