Identification of the Vitamin B₁₂-Binding Protein in the Serum of Normals and of Patients with Chronic Myelocytic Leukemia

Vitamin B₁₂-binding proteins in the serum of normal subjects and of patients with chronic myelocytic leukemia have been compared. The in-vivo-bound B₁₂ was utilized to identify the binding protein. Column protein chromatography and block and paper electrophoresis were employed individually and in combination to characterize the B₁₂-binding protein.

B₁₂ was found to be bound primarily to an alpha-l globulin in both normal individuals and in patients with chronic myelocytic leukemia. No qualitative difference was found in these proteins.

The increased amounts of B₁₂-binding protein in the serum of patients with chronic myelocytic leukemia would seem to be attributable to abnormal metabolism of the same protein that binds B₁₂ in normal serum.