Studies on a fraction of human gastric mucosa containing intrinsic factor isoproteins typical of mucosa.Scand J Clin Lab Invest. 1975 Jan; 35(1):13-8.SJ
A mucosal fraction containing isoproteins of the vitamin B12-intrinsic factor complex with high isoelectric points (pH 5.95-6.52) was prepared, using DEAE-cellulose chromatography. It possessed biological and immunological intrinsic factor activity, and its molecular weight was about 2,000 daltons smaller than that of the isoprotein assembly of gastric juice. Neuraminidase digestion of the gastric juice complex produced a biologically active product containing the high pI isoproteins typical of mucosa. Thus the high pI fraction is deficient in sialic acid, apparently consisting of 'incomplete' molecules not yet ready to be secreted.