Effect of Proteolytic Enzymes on the Binding of Cobalamin to R Protein and Intrinsic Factor

Abstract

A B S T R A C T Cobalamin (Cbl; vitamin B,2) malab- sorption in pancreatic insufficiency can be partially cor- rected by bicarbonate and completely corrected by pancreatic proteases but the mechanisms involved are unknown. Because saliva contains enough R-type Cbl- binding protein (R protein) to bind all of the dietary and biliary Cbl, it is possible that R protein acts as an inhibitor of Cbl absorption and that pancreatic pro- teases are required to alter R protein and prevent such inhibition. To test this hypothesis we studied the abil- ity of R protein and intrinsic factor (IF) to compete for Cbl binding and ability of pancreatic proteases to alter this competition.