Newly identified iron-binding protein in human duodenal mucosa.

Studies were undertaken using human duodenal mucosa to determine whether it contained a counterpart to a newly identified iron-binding protein recently isolated from rat duodenum and named mobilferrin. Water-soluble homogenates were prepared from duodena of patients undergoing surgery for pancreatic carcinoma. An iron-binding protein with an approximate molecular mass of 56 Kd was purified to homogeneity using 60% ammonium sulfate and serial chromatographic steps. The protein was biochemically and immunologically distinct from transferrin and ferritin, and competitively bound to zinc, cobalt, and lead. Each molecule bound one molecule of iron with a kd of 8.9 x 10(-5). Human isolates reacted in an enzyme-linked immunosorbent assay with a polyclonal antibody raised in rabbits against a similar duodenal protein isolated from rat duodenum. It is postulated that mobilferrin plays a significant role in the absorption of iron and other metals and may explain partially the competition between certain metals for absorption in the small intestine.